diff --git a/src/features/online-board/api.ts b/src/features/online-board/api.ts
index 27b26f64..6234a877 100644
--- a/src/features/online-board/api.ts
+++ b/src/features/online-board/api.ts
@@ -66,6 +66,7 @@ export interface CalendarParams {
 export async function searchFlights(
   client: ApiClient,
   params: SearchFlightsParams,
+  signal?: AbortSignal,
 ): Promise<IBoardResponse> {
   const query: Record<string, string> = {
     dateFrom: params.dateFrom,
@@ -78,7 +79,7 @@ export async function searchFlights(
   if (params.timeFrom) query["timeFrom"] = params.timeFrom;
   if (params.timeTo) query["timeTo"] = params.timeTo;
 
-  return client.get<IBoardResponse>(`flights/v1.1/${client.locale}/board`, query);
+  return client.get<IBoardResponse>(`flights/v1.1/${client.locale}/board`, query, signal);
 }
 
 /**
diff --git a/src/features/online-board/components/OnlineBoardFilter.tsx b/src/features/online-board/components/OnlineBoardFilter.tsx
index 3eb17e0f..a32c8d60 100644
--- a/src/features/online-board/components/OnlineBoardFilter.tsx
+++ b/src/features/online-board/components/OnlineBoardFilter.tsx
@@ -8,7 +8,7 @@
  * @module
  */
 
-import { type FC, useState, useCallback, useEffect, useRef, type FormEvent } from "react";
+import { type FC, useState, useCallback, useEffect, useRef, type FormEvent, useMemo } from "react";
 import { useNavigate } from "@modern-js/runtime/router";
 import { useLocale } from "@/i18n/useLocale.js";
 import { Calendar } from "primereact/calendar";
@@ -150,6 +150,23 @@ export const OnlineBoardFilter: FC<OnlineBoardFilterProps> = ({
   const boardMinDate = useRef(getBoardMinDate()).current;
   const boardMaxDate = useRef(getBoardMaxDate()).current;
 
+  // §4.1.10 — submit button locked for 30 seconds after each search.
+  // Value is the timestamp when the lock expires (or 0 if unlocked).
+  // The 30-second constant is intentionally hardcoded (not configurable).
+  const [submitLockedUntil, setSubmitLockedUntil] = useState(0);
+  const [now, setNow] = useState(() => Date.now());
+  // Tick every second while the lock is active so the disabled state
+  // updates reactively.
+  useEffect(() => {
+    if (submitLockedUntil === 0 || now >= submitLockedUntil) return;
+    const id = setTimeout(() => setNow(Date.now()), 1000);
+    return () => clearTimeout(id);
+  }, [submitLockedUntil, now]);
+  const isSubmitLocked = useMemo(
+    () => submitLockedUntil > 0 && now < submitLockedUntil,
+    [submitLockedUntil, now],
+  );
+
   // Swap the Calendar input's display text to "Сегодня" / "Завтра" per
   // TZ §4.1.9 Tables 11+12 — Angular ships this and the raw 'DD.MM.YYYY'
   // reads clinical in comparison.
@@ -227,6 +244,7 @@ export const OnlineBoardFilter: FC<OnlineBoardFilterProps> = ({
   const handleFlightSubmit = useCallback(
     (e: FormEvent) => {
       e.preventDefault();
+      if (isSubmitLocked) return;
 
       const error = validateFlightNumber(flightNumber);
       setFlightNumberError(error);
@@ -250,15 +268,20 @@ export const OnlineBoardFilter: FC<OnlineBoardFilterProps> = ({
         searchExecuted: true,
       });
 
+      // Lock submit for 30 seconds (§4.1.10 — hardcoded, not configurable)
+      setSubmitLockedUntil(Date.now() + 30_000);
+      setNow(Date.now());
+
       const url = buildOnlineBoardUrl({ type: "flight", carrier, flightNumber: num, date: dateParam });
       void navigate(`/${locale}/${url}`);
     },
-    [flightNumber, flightDate, navigate, locale],
+    [flightNumber, flightDate, navigate, locale, isSubmitLocked],
   );
 
   const handleRouteSubmit = useCallback(
     (e: FormEvent) => {
       e.preventDefault();
+      if (isSubmitLocked) return;
 
       // Mirrors Angular's OnlineBoardFilterService.toRoutePage + the
       // UrlBuilder.getRoutePageUrl switch: one-sided searches (only
@@ -324,9 +347,12 @@ export const OnlineBoardFilter: FC<OnlineBoardFilterProps> = ({
         });
         url = buildOnlineBoardUrl({ type: "route", departure: depCode, arrival: arrCode, date: dateParam, ...timeExtras });
       }
+      // Lock submit for 30 seconds (§4.1.10 — hardcoded, not configurable)
+      setSubmitLockedUntil(Date.now() + 30_000);
+      setNow(Date.now());
       void navigate(`/${locale}/${url}`);
     },
-    [routeDepartureCode, routeArrivalCode, routeDate, timeRange, navigate, locale],
+    [routeDepartureCode, routeArrivalCode, routeDate, timeRange, navigate, locale, isSubmitLocked],
   );
 
   return (
@@ -452,6 +478,8 @@ export const OnlineBoardFilter: FC<OnlineBoardFilterProps> = ({
                       type="submit"
                       className="search-button"
                       data-testid="search-submit"
+                      disabled={isSubmitLocked}
+                      aria-disabled={isSubmitLocked}
                     >
                       <span>{t("SHARED.SEARCH")}</span>
                     </button>
@@ -622,6 +650,8 @@ export const OnlineBoardFilter: FC<OnlineBoardFilterProps> = ({
                       type="submit"
                       className="search-button"
                       data-testid="search-submit"
+                      disabled={isSubmitLocked}
+                      aria-disabled={isSubmitLocked}
                     >
                       <span>{t("SHARED.SEARCH")}</span>
                     </button>
diff --git a/src/features/online-board/components/OnlineBoardSearchPage.error.test.tsx b/src/features/online-board/components/OnlineBoardSearchPage.error.test.tsx
new file mode 100644
index 00000000..d55fdec1
--- /dev/null
+++ b/src/features/online-board/components/OnlineBoardSearchPage.error.test.tsx
@@ -0,0 +1,150 @@
+/**
+ * Tests for per-status error messages in OnlineBoardSearchPage — TZ §4.1.10.1 / §4.1.12
+ *
+ * @vitest-environment jsdom
+ */
+
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { render, screen } from "@testing-library/react";
+import type { OnlineBoardSearchPageProps } from "./OnlineBoardSearchPage.js";
+import { ApiHttpError, ApiTimeoutError } from "@/shared/api/errors.js";
+import type { UseOnlineBoardResult } from "../hooks/useOnlineBoard.js";
+
+// ── shared mocks ──────────────────────────────────────────────────────────────
+
+vi.mock("@/i18n/provider.js", () => ({
+  useTranslation: () => ({
+    t: (key: string) => key,
+    i18n: { language: "ru" },
+  }),
+}));
+
+vi.mock("@modern-js/runtime/router", () => ({
+  useNavigate: () => vi.fn(),
+  useParams: () => ({ lang: "ru-ru" }),
+  Link: ({ children, ...props }: Record<string, unknown>) =>
+    <a {...props}>{children as React.ReactNode}</a>,
+}));
+
+vi.mock("@/ui/layout/PageTabs.js", () => ({
+  PageTabs: () => <div data-testid="page-tabs" />,
+}));
+
+vi.mock("./OnlineBoardFilter.js", () => ({
+  OnlineBoardFilter: () => <div data-testid="online-board-filter" />,
+}));
+
+vi.mock("@/shared/hooks/useSearchHistory.js", () => ({
+  useSearchHistory: () => ({ items: [], add: vi.fn(), clear: vi.fn() }),
+}));
+
+vi.mock("@/features/flights-map/hooks/useFeatureFlag.js", () => ({
+  useFeatureFlag: () => false,
+}));
+
+vi.mock("../hooks/useLiveBoardSearch.js", () => ({
+  useLiveBoardSearch: (_params: unknown, initialFlights: unknown) => ({
+    flights: initialFlights,
+    connectionStatus: "idle" as const,
+  }),
+}));
+
+vi.mock("../hooks/useCalendarDays.js", () => ({
+  useCalendarDays: () => ({ days: [], loading: false }),
+}));
+
+vi.mock("@/shared/dictionaries/index.js", () => ({
+  useDictionaries: () => ({ dictionaries: null, loading: false, error: null }),
+}));
+
+// Hoisted mock for useOnlineBoard — overridden per test
+const mockUseOnlineBoard = vi.fn<() => UseOnlineBoardResult>();
+vi.mock("../hooks/useOnlineBoard.js", () => ({
+  useOnlineBoard: () => mockUseOnlineBoard(),
+}));
+
+// ── fixtures ──────────────────────────────────────────────────────────────────
+
+const DEPARTURE_PARAMS: OnlineBoardSearchPageProps["params"] = {
+  type: "departure",
+  station: "SVO",
+  date: "20260115",
+};
+
+function noResult(): UseOnlineBoardResult {
+  return {
+    flights: [],
+    loading: false,
+    error: null,
+    refresh: vi.fn(),
+    cancel: vi.fn(),
+  };
+}
+
+// ── tests ─────────────────────────────────────────────────────────────────────
+
+describe("OnlineBoardSearchPage — §4.1.10.1 per-status error messages", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("shows BOARD.ERROR-TIMEOUT for ApiTimeoutError", async () => {
+    // Dynamic import so the mock is already in place
+    const { OnlineBoardSearchPage } = await import("./OnlineBoardSearchPage.js");
+
+    mockUseOnlineBoard.mockReturnValue({
+      ...noResult(),
+      error: new ApiTimeoutError(30_000),
+    });
+
+    render(<OnlineBoardSearchPage params={DEPARTURE_PARAMS} />);
+    expect(screen.getByTestId("search-error")).toBeTruthy();
+    expect(screen.getByText("BOARD.ERROR-TIMEOUT")).toBeTruthy();
+  });
+
+  it("shows BOARD.ERROR-5XX for ApiHttpError with status 5xx", async () => {
+    const { OnlineBoardSearchPage } = await import("./OnlineBoardSearchPage.js");
+
+    mockUseOnlineBoard.mockReturnValue({
+      ...noResult(),
+      error: new ApiHttpError("Server error", 503),
+    });
+
+    render(<OnlineBoardSearchPage params={DEPARTURE_PARAMS} />);
+    expect(screen.getByText("BOARD.ERROR-5XX")).toBeTruthy();
+  });
+
+  it("shows BOARD.ERROR-4XX for ApiHttpError with status 4xx", async () => {
+    const { OnlineBoardSearchPage } = await import("./OnlineBoardSearchPage.js");
+
+    mockUseOnlineBoard.mockReturnValue({
+      ...noResult(),
+      error: new ApiHttpError("Not found", 404),
+    });
+
+    render(<OnlineBoardSearchPage params={DEPARTURE_PARAMS} />);
+    expect(screen.getByText("BOARD.ERROR-4XX")).toBeTruthy();
+  });
+
+  it("shows cancel button while loading (§4.1.12)", async () => {
+    const { OnlineBoardSearchPage } = await import("./OnlineBoardSearchPage.js");
+
+    mockUseOnlineBoard.mockReturnValue({
+      ...noResult(),
+      loading: true,
+    });
+
+    render(<OnlineBoardSearchPage params={DEPARTURE_PARAMS} />);
+    expect(screen.getByTestId("cancel-search-btn")).toBeTruthy();
+    expect(screen.getByText("SHARED.SEARCH-CANCEL")).toBeTruthy();
+  });
+
+  it("hides cancel button when not loading (§4.1.12)", async () => {
+    const { OnlineBoardSearchPage } = await import("./OnlineBoardSearchPage.js");
+
+    mockUseOnlineBoard.mockReturnValue(noResult());
+
+    render(<OnlineBoardSearchPage params={DEPARTURE_PARAMS} />);
+    expect(screen.queryByTestId("cancel-search-btn")).toBeNull();
+  });
+});
diff --git a/src/features/online-board/components/OnlineBoardSearchPage.scss b/src/features/online-board/components/OnlineBoardSearchPage.scss
index 30fc049d..df713faa 100644
--- a/src/features/online-board/components/OnlineBoardSearchPage.scss
+++ b/src/features/online-board/components/OnlineBoardSearchPage.scss
@@ -72,6 +72,41 @@
     display: none;
   }
 
+  // §4.1.12 — loader bar with cancel button, shown while search is running
+  &__loader-bar {
+    display: flex;
+    justify-content: center;
+    padding: vars.$space-m vars.$space-xl;
+  }
+
+  &__cancel-btn {
+    display: inline-block;
+    padding: vars.$space-s2 vars.$space-xl;
+    background-color: colors.$blue-light;
+    color: colors.$white;
+    border: none;
+    border-radius: vars.$border-radius;
+    cursor: pointer;
+    font-size: fonts.$font-size-m;
+    font-weight: fonts.$font-medium;
+    transition: background-color 0.2s ease;
+
+    &:hover {
+      background-color: colors.$blue-light--hover;
+    }
+  }
+
+  // §4.1.10 — while search is running, block interactions with filter,
+  // tabs, and breadcrumbs so the user cannot start a conflicting search.
+  &[data-searching="true"] {
+    .page-layout__left,
+    .page-layout__sticky,
+    .page-layout__breadcrumbs {
+      pointer-events: none;
+      opacity: 0.6;
+    }
+  }
+
   // Mirrors Angular `page-footer-notes` under `pages/schedule/home.scss`:
   // a blue-extra-light card attached to the bottom of the flight-list
   // frame, with a small `*` sort-note aligned to an inner line holding
diff --git a/src/features/online-board/components/OnlineBoardSearchPage.tsx b/src/features/online-board/components/OnlineBoardSearchPage.tsx
index b61f2e71..8628e281 100644
--- a/src/features/online-board/components/OnlineBoardSearchPage.tsx
+++ b/src/features/online-board/components/OnlineBoardSearchPage.tsx
@@ -14,6 +14,7 @@
 
 import type { FC } from "react";
 import { useCallback, useEffect } from "react";
+import { ApiHttpError, ApiTimeoutError } from "@/shared/api/errors.js";
 import { useNavigate } from "@modern-js/runtime/router";
 import { useLocale } from "@/i18n/useLocale.js";
 import { useTranslation } from "@/i18n/provider.js";
@@ -334,7 +335,17 @@ export const OnlineBoardSearchPage: FC<OnlineBoardSearchPageProps> = ({
 
   // Data fetching
   const searchParams = toSearchParams(params);
-  const { flights, loading, error, refresh } = useOnlineBoard(searchParams);
+  const { flights, loading, error, refresh, cancel } = useOnlineBoard(searchParams);
+
+  // §4.1.12 — Escape cancels while loader is showing
+  useEffect(() => {
+    if (!loading) return;
+    const handleKeyDown = (e: KeyboardEvent) => {
+      if (e.key === "Escape") cancel();
+    };
+    document.addEventListener("keydown", handleKeyDown);
+    return () => document.removeEventListener("keydown", handleKeyDown);
+  }, [loading, cancel]);
 
   // Live updates via SignalR
   const liveBoardParams = toLiveBoardParams(params);
@@ -401,8 +412,23 @@ export const OnlineBoardSearchPage: FC<OnlineBoardSearchPageProps> = ({
     ? buildFlightListJsonLd(displayFlights, searchDescription)
     : undefined;
 
+  // §4.1.10.1 — resolve per-status error message key
+  const errorMessageKey = (() => {
+    if (!error) return null;
+    if (error instanceof ApiTimeoutError) return "BOARD.ERROR-TIMEOUT";
+    if (error instanceof ApiHttpError) {
+      return error.status >= 500 ? "BOARD.ERROR-5XX" : "BOARD.ERROR-4XX";
+    }
+    return "BOARD.LOAD-FAILED-MESSAGE";
+  })();
+
   return (
-    <div className="online-board-search" data-testid="online-board-search">
+    <div
+      className="online-board-search"
+      data-testid="online-board-search"
+      // §4.1.10 — flag so CSS can pointer-events:none filter/tabs/breadcrumbs
+      data-searching={loading ? "true" : undefined}
+    >
       {jsonLd && <JsonLdRenderer data={jsonLd} />}
       <PageLayout
         headerLeft={<PageTabs viewType="onlineboard" />}
@@ -491,7 +517,21 @@ export const OnlineBoardSearchPage: FC<OnlineBoardSearchPageProps> = ({
           )}
         </div>
 
-        {/* Error state */}
+        {/* §4.1.12 — Cancel search button: visible while loading */}
+        {loading && (
+          <div className="online-board-search__loader-bar" data-testid="loader-bar">
+            <button
+              type="button"
+              className="online-board-search__cancel-btn"
+              data-testid="cancel-search-btn"
+              onClick={cancel}
+            >
+              {t("SHARED.SEARCH-CANCEL")}
+            </button>
+          </div>
+        )}
+
+        {/* §4.1.10.1 — Error state with per-status message */}
         {error && (
           <section className="frame" data-testid="search-error" role="alert">
             <div className="online-board-search__error-card">
@@ -499,7 +539,7 @@ export const OnlineBoardSearchPage: FC<OnlineBoardSearchPageProps> = ({
                 {t("BOARD.LOAD-FAILED-TITLE")}
               </h3>
               <p className="online-board-search__error-message">
-                {t("BOARD.LOAD-FAILED-MESSAGE")}
+                {t(errorMessageKey ?? "BOARD.LOAD-FAILED-MESSAGE")}
               </p>
               <button
                 type="button"
diff --git a/src/features/online-board/hooks/useOnlineBoard.test.ts b/src/features/online-board/hooks/useOnlineBoard.test.ts
new file mode 100644
index 00000000..3eedf828
--- /dev/null
+++ b/src/features/online-board/hooks/useOnlineBoard.test.ts
@@ -0,0 +1,119 @@
+/**
+ * Unit tests for useOnlineBoard hook — TZ §4.1.10, §4.1.12
+ *
+ * Covers:
+ * - AbortController wired: new search aborts the previous in-flight request
+ * - cancel() aborts the controller and resets loading
+ *
+ * @vitest-environment jsdom
+ */
+
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import { renderHook, act } from "@testing-library/react";
+import type { ReactNode } from "react";
+import React from "react";
+import { useOnlineBoard } from "./useOnlineBoard.js";
+import * as api from "../api.js";
+import type { IBoardResponse } from "../types.js";
+import { ApiClientProvider } from "@/shared/api/provider.js";
+import type { ApiClient } from "@/shared/api/client.js";
+
+// Minimal mock API client
+function makeClient(): ApiClient {
+  return {
+    locale: "ru",
+    get: vi.fn(),
+    post: vi.fn(),
+  } as unknown as ApiClient;
+}
+
+function makeWrapper(client: ApiClient) {
+  return function Wrapper({ children }: { children: ReactNode }) {
+    return React.createElement(ApiClientProvider, { client, children });
+  };
+}
+
+const EMPTY_RESPONSE: IBoardResponse = {
+  data: { routes: [], partners: [] },
+};
+
+describe("useOnlineBoard — §4.1.12 cancellation", () => {
+  const baseParams = {
+    dateFrom: "2026-01-15T00:00:00",
+    dateTo: "2026-01-16T00:00:00",
+    departure: "SVO",
+  };
+
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("passes AbortSignal to searchFlights", async () => {
+    const client = makeClient();
+    const spy = vi.spyOn(api, "searchFlights").mockResolvedValue(EMPTY_RESPONSE);
+
+    renderHook(() => useOnlineBoard(baseParams), {
+      wrapper: makeWrapper(client),
+    });
+
+    // Wait for the async effect
+    await act(async () => {
+      await Promise.resolve();
+    });
+
+    expect(spy).toHaveBeenCalledOnce();
+    const [, , signal] = spy.mock.calls[0] as [unknown, unknown, AbortSignal | undefined];
+    expect(signal).toBeInstanceOf(AbortSignal);
+  });
+
+  it("cancel() aborts the request and sets loading to false", async () => {
+    const client = makeClient();
+    // Never resolve — simulates a slow in-flight request
+    vi.spyOn(api, "searchFlights").mockReturnValue(new Promise(() => {}));
+
+    const { result } = renderHook(() => useOnlineBoard(baseParams), {
+      wrapper: makeWrapper(client),
+    });
+
+    // Should be loading initially
+    expect(result.current.loading).toBe(true);
+
+    act(() => {
+      result.current.cancel();
+    });
+
+    expect(result.current.loading).toBe(false);
+  });
+
+  it("new param change aborts the previous in-flight request (§4.1.12)", async () => {
+    const client = makeClient();
+    const capturedSignals: AbortSignal[] = [];
+
+    vi.spyOn(api, "searchFlights").mockImplementation((_c, _p, signal) => {
+      if (signal) capturedSignals.push(signal);
+      return new Promise(() => {}); // Never resolves
+    });
+
+    const { rerender } = renderHook(
+      (params) => useOnlineBoard(params),
+      {
+        initialProps: baseParams,
+        wrapper: makeWrapper(client),
+      },
+    );
+
+    // Wait for first effect
+    await act(async () => { await Promise.resolve(); });
+    expect(capturedSignals).toHaveLength(1);
+
+    // Change params — triggers new effect which aborts the old controller
+    rerender({ ...baseParams, departure: "LED" });
+    await act(async () => { await Promise.resolve(); });
+
+    // First signal should now be aborted
+    expect(capturedSignals[0]?.aborted).toBe(true);
+    // Second request was started with a fresh (non-aborted) controller
+    expect(capturedSignals).toHaveLength(2);
+    expect(capturedSignals[1]?.aborted).toBe(false);
+  });
+});
diff --git a/src/features/online-board/hooks/useOnlineBoard.ts b/src/features/online-board/hooks/useOnlineBoard.ts
index ce2bf477..17aa16d0 100644
--- a/src/features/online-board/hooks/useOnlineBoard.ts
+++ b/src/features/online-board/hooks/useOnlineBoard.ts
@@ -2,6 +2,7 @@
  * React hook for the online board search pages.
  *
  * Calls `searchFlights` on param change, manages loading/error/data state.
+ * Supports AbortController-based cancellation (§4.1.12).
  * Thin wrapper — integration-tested by 2E/2H, not unit-tested here.
  *
  * @module
@@ -19,11 +20,13 @@ export interface UseOnlineBoardResult {
   loading: boolean;
   error: ApiError | null;
   refresh: () => void;
+  /** Cancel the in-flight request (§4.1.12). Resets loading to false. */
+  cancel: () => void;
 }
 
 /**
  * Hook for online board search pages. Fetches flights based on search params
- * and provides refresh capability.
+ * and provides refresh + cancel capability.
  */
 export function useOnlineBoard(
   params: SearchFlightsParams,
@@ -38,10 +41,21 @@ export function useOnlineBoard(
   const paramsRef = useRef(params);
   paramsRef.current = params;
 
+  // AbortController for the current in-flight request (§4.1.12)
+  const abortRef = useRef<AbortController | null>(null);
+
   const refresh = useCallback(() => {
     setRefreshKey((k) => k + 1);
   }, []);
 
+  const cancel = useCallback(() => {
+    if (abortRef.current) {
+      abortRef.current.abort();
+      abortRef.current = null;
+    }
+    setLoading(false);
+  }, []);
+
   useEffect(() => {
     // Callers pass empty strings when the search context isn't resolved
     // yet (e.g. details page with no `?request=...`). Skip the fetch
@@ -54,27 +68,34 @@ export function useOnlineBoard(
       return;
     }
 
-    let cancelled = false;
+    // Abort any previous in-flight request (§4.1.12 — new search aborts in-flight)
+    if (abortRef.current) {
+      abortRef.current.abort();
+    }
+    const controller = new AbortController();
+    abortRef.current = controller;
+
     setLoading(true);
     setError(null);
 
-    searchFlights(client, paramsRef.current)
+    searchFlights(client, paramsRef.current, controller.signal)
       .then((response) => {
-        if (!cancelled) {
+        if (!controller.signal.aborted) {
           setFlights(response.data?.routes ?? []);
           setLoading(false);
         }
       })
       .catch((err: unknown) => {
+        // Ignore aborted requests — the user cancelled intentionally
+        if (controller.signal.aborted) return;
         console.error("[useOnlineBoard] API error:", err);
-        if (!cancelled) {
-          setError(err as ApiError);
-          setLoading(false);
-        }
+        setError(err as ApiError);
+        setLoading(false);
       });
 
     return () => {
-      cancelled = true;
+      controller.abort();
+      abortRef.current = null;
     };
   }, [
     client,
@@ -88,5 +109,5 @@ export function useOnlineBoard(
     refreshKey,
   ]);
 
-  return { flights, loading, error, refresh };
+  return { flights, loading, error, refresh, cancel };
 }
diff --git a/src/features/schedule/api.ts b/src/features/schedule/api.ts
index 07cdc2be..448837e2 100644
--- a/src/features/schedule/api.ts
+++ b/src/features/schedule/api.ts
@@ -33,6 +33,7 @@ import type {
 export async function searchSchedule(
   client: ApiClient,
   params: IScheduleSearchRequest,
+  signal?: AbortSignal,
 ): Promise<IScheduleResponse> {
   const query: Record<string, string> = {
     departure: params.departure,
@@ -47,6 +48,7 @@ export async function searchSchedule(
   return client.get<IScheduleResponse>(
     `flights/1/${client.locale}/schedule`,
     query,
+    signal,
   );
 }
 
diff --git a/src/features/schedule/components/ScheduleFilter.tsx b/src/features/schedule/components/ScheduleFilter.tsx
index 9836f818..702ca3b2 100644
--- a/src/features/schedule/components/ScheduleFilter.tsx
+++ b/src/features/schedule/components/ScheduleFilter.tsx
@@ -8,7 +8,7 @@
  * search is route-only.
  */
 
-import { type FC, useState, useCallback, useRef, useEffect, type FormEvent } from "react";
+import { type FC, useState, useCallback, useRef, useEffect, useMemo, type FormEvent } from "react";
 import { useNavigate } from "@modern-js/runtime/router";
 import { Calendar } from "primereact/calendar";
 import { Slider, type SliderChangeEvent } from "primereact/slider";
@@ -136,6 +136,20 @@ export const ScheduleFilter: FC<ScheduleFilterProps> = ({
   const scheduleMinDate = useRef(getScheduleMinDate()).current;
   const scheduleMaxDate = useRef(getScheduleMaxDate()).current;
 
+  // §4.1.11 — submit button locked for 30 seconds after each search.
+  // The 30-second constant is intentionally hardcoded (not configurable).
+  const [submitLockedUntil, setSubmitLockedUntil] = useState(0);
+  const [nowTs, setNowTs] = useState(() => Date.now());
+  useEffect(() => {
+    if (submitLockedUntil === 0 || nowTs >= submitLockedUntil) return;
+    const id = setTimeout(() => setNowTs(Date.now()), 1000);
+    return () => clearTimeout(id);
+  }, [submitLockedUntil, nowTs]);
+  const isSubmitLocked = useMemo(
+    () => submitLockedUntil > 0 && nowTs < submitLockedUntil,
+    [submitLockedUntil, nowTs],
+  );
+
   // Swap the Calendar input's displayed text to "Текущая неделя" per
   // TZ §4.1.9 Table 14 when the selected range equals Mon-Sun of the
   // current week. Uses inputRef + useEffect to override PrimeReact's
@@ -159,6 +173,7 @@ export const ScheduleFilter: FC<ScheduleFilterProps> = ({
   const handleSubmit = useCallback(
     (e: FormEvent<HTMLFormElement>) => {
       e.preventDefault();
+      if (isSubmitLocked) return;
       const dep = departure.trim().toUpperCase();
       const arr = arrival.trim().toUpperCase();
       if (!dep || !arr) return;
@@ -258,6 +273,9 @@ export const ScheduleFilter: FC<ScheduleFilterProps> = ({
         params = { type: "route", outbound };
       }
       const url = buildScheduleUrl(params);
+      // Lock submit for 30 seconds (§4.1.11 — hardcoded, not configurable)
+      setSubmitLockedUntil(Date.now() + 30_000);
+      setNowTs(Date.now());
       void navigate(`/${locale}/${url}`);
     },
     [
@@ -271,6 +289,7 @@ export const ScheduleFilter: FC<ScheduleFilterProps> = ({
       returnTimeRange,
       navigate,
       locale,
+      isSubmitLocked,
     ],
   );
 
@@ -531,6 +550,8 @@ export const ScheduleFilter: FC<ScheduleFilterProps> = ({
               type="submit"
               className="search-button"
               data-testid="search-submit"
+              disabled={isSubmitLocked}
+              aria-disabled={isSubmitLocked}
             >
               <span>{t("SHARED.SCHEDULES_VIEW")}</span>
             </button>
diff --git a/src/features/schedule/components/ScheduleSearchPage.scss b/src/features/schedule/components/ScheduleSearchPage.scss
index b7e96377..e9f3c57d 100644
--- a/src/features/schedule/components/ScheduleSearchPage.scss
+++ b/src/features/schedule/components/ScheduleSearchPage.scss
@@ -16,6 +16,40 @@
     color: colors.$red;
   }
 
+  // §4.1.12 — loader bar with cancel button
+  &__loader-bar {
+    display: flex;
+    justify-content: center;
+    padding: vars.$space-m vars.$space-xl;
+  }
+
+  &__cancel-btn {
+    display: inline-block;
+    padding: vars.$space-s2 vars.$space-xl;
+    background-color: colors.$blue-light;
+    color: colors.$white;
+    border: none;
+    border-radius: vars.$border-radius;
+    cursor: pointer;
+    font-size: fonts.$font-size-m;
+    font-weight: fonts.$font-medium;
+    transition: background-color 0.2s ease;
+
+    &:hover {
+      background-color: colors.$blue-light--hover;
+    }
+  }
+
+  // §4.1.11 — block filter/tabs/breadcrumbs while loading
+  &[data-searching="true"] {
+    .page-layout__left,
+    .page-layout__sticky,
+    .page-layout__breadcrumbs {
+      pointer-events: none;
+      opacity: 0.6;
+    }
+  }
+
   &__outbound,
   &__inbound {
     padding: vars.$space-xl 0;
diff --git a/src/features/schedule/components/ScheduleSearchPage.tsx b/src/features/schedule/components/ScheduleSearchPage.tsx
index f5c2b56f..f838dd30 100644
--- a/src/features/schedule/components/ScheduleSearchPage.tsx
+++ b/src/features/schedule/components/ScheduleSearchPage.tsx
@@ -10,6 +10,7 @@
 
 import type { FC } from "react";
 import { useCallback, useEffect, useState } from "react";
+import { ApiHttpError, ApiTimeoutError } from "@/shared/api/errors.js";
 import { useNavigate } from "@modern-js/runtime/router";
 import { useLocale } from "@/i18n/useLocale.js";
 import { useTranslation } from "@/i18n/provider.js";
@@ -263,7 +264,7 @@ export const ScheduleSearchPage: FC<ScheduleSearchPageProps> = ({ params }) => {
 
   // Fetch outbound flights
   const outboundRequest = toSearchRequest(outbound);
-  const { flights: outboundFlights, loading: outboundLoading, error: outboundError, refresh } =
+  const { flights: outboundFlights, loading: outboundLoading, error: outboundError, refresh, cancel: cancelOutbound } =
     useScheduleSearch(outboundRequest);
 
   // Fetch inbound flights (if round-trip)
@@ -271,9 +272,36 @@ export const ScheduleSearchPage: FC<ScheduleSearchPageProps> = ({ params }) => {
   const {
     flights: inboundFlights,
     loading: inboundLoading,
+    cancel: cancelInbound,
   } = useScheduleSearch(inboundRequest);
 
-  const _loading = outboundLoading || (inbound ? inboundLoading : false);
+  const isLoading = outboundLoading || (inbound ? inboundLoading : false);
+
+  // §4.1.12 — cancel both directions at once
+  const cancel = useCallback(() => {
+    cancelOutbound();
+    cancelInbound();
+  }, [cancelOutbound, cancelInbound]);
+
+  // §4.1.12 — Escape cancels while loader is showing
+  useEffect(() => {
+    if (!isLoading) return;
+    const handleKeyDown = (e: KeyboardEvent) => {
+      if (e.key === "Escape") cancel();
+    };
+    document.addEventListener("keydown", handleKeyDown);
+    return () => document.removeEventListener("keydown", handleKeyDown);
+  }, [isLoading, cancel]);
+
+  // §4.1.11.1 — per-status error message key
+  const errorMessageKey = (() => {
+    if (!outboundError) return null;
+    if (outboundError instanceof ApiTimeoutError) return "BOARD.ERROR-TIMEOUT";
+    if (outboundError instanceof ApiHttpError) {
+      return outboundError.status >= 500 ? "BOARD.ERROR-5XX" : "BOARD.ERROR-4XX";
+    }
+    return "BOARD.LOAD-FAILED";
+  })();
 
   /** Navigate to a different week (Monday → Sunday range). Updates the
    *  active direction's params and preserves the other direction. */
@@ -340,7 +368,12 @@ export const ScheduleSearchPage: FC<ScheduleSearchPageProps> = ({ params }) => {
     : undefined;
 
   return (
-    <div className="schedule-search" data-testid="schedule-search">
+    <div
+      className="schedule-search"
+      data-testid="schedule-search"
+      // §4.1.11 — block filter/tabs/breadcrumbs while searching
+      data-searching={isLoading ? "true" : undefined}
+    >
       {jsonLd && <JsonLdRenderer data={jsonLd} />}
       <PageLayout
         headerLeft={<PageTabs viewType="schedule" />}
@@ -435,10 +468,25 @@ export const ScheduleSearchPage: FC<ScheduleSearchPageProps> = ({ params }) => {
           </>
         }
       >
+        {/* §4.1.12 — cancel button visible while loading */}
+        {isLoading && (
+          <div className="schedule-search__loader-bar" data-testid="loader-bar">
+            <button
+              type="button"
+              className="schedule-search__cancel-btn"
+              data-testid="cancel-search-btn"
+              onClick={cancel}
+            >
+              {t("SHARED.SEARCH-CANCEL")}
+            </button>
+          </div>
+        )}
+
+        {/* §4.1.11.1 — per-status error message */}
         {outboundError && (
-          <section className="frame" data-testid="search-error">
+          <section className="frame" data-testid="search-error" role="alert">
             <div className="schedule-search__error">
-              <p>{t("BOARD.LOAD-FAILED")}</p>
+              <p>{t(errorMessageKey ?? "BOARD.LOAD-FAILED")}</p>
               <button type="button" onClick={refresh}>{t("SHARED.RETRY")}</button>
             </div>
           </section>
diff --git a/src/features/schedule/hooks/useScheduleSearch.ts b/src/features/schedule/hooks/useScheduleSearch.ts
index 15cfab7e..718c7c22 100644
--- a/src/features/schedule/hooks/useScheduleSearch.ts
+++ b/src/features/schedule/hooks/useScheduleSearch.ts
@@ -2,6 +2,7 @@
  * React hook for schedule search pages.
  *
  * Calls `searchSchedule` on param change, manages loading/error/data state.
+ * Supports AbortController-based cancellation (§4.1.12).
  * No SignalR -- schedule data is static.
  *
  * @module
@@ -18,11 +19,13 @@ export interface UseScheduleSearchResult {
   loading: boolean;
   error: ApiError | null;
   refresh: () => void;
+  /** Cancel the in-flight request (§4.1.12). Resets loading to false. */
+  cancel: () => void;
 }
 
 /**
  * Hook for schedule search pages. Fetches flights based on search params
- * and provides refresh capability.
+ * and provides refresh + cancel capability.
  */
 export function useScheduleSearch(
   params: IScheduleSearchRequest,
@@ -36,31 +39,49 @@ export function useScheduleSearch(
   const paramsRef = useRef(params);
   paramsRef.current = params;
 
+  // AbortController for the current in-flight request (§4.1.12)
+  const abortRef = useRef<AbortController | null>(null);
+
   const refresh = useCallback(() => {
     setRefreshKey((k) => k + 1);
   }, []);
 
+  const cancel = useCallback(() => {
+    if (abortRef.current) {
+      abortRef.current.abort();
+      abortRef.current = null;
+    }
+    setLoading(false);
+  }, []);
+
   useEffect(() => {
-    let cancelled = false;
+    // Abort any previous in-flight request (§4.1.12 — new search aborts in-flight)
+    if (abortRef.current) {
+      abortRef.current.abort();
+    }
+    const controller = new AbortController();
+    abortRef.current = controller;
+
     setLoading(true);
     setError(null);
 
-    searchSchedule(client, paramsRef.current)
+    searchSchedule(client, paramsRef.current, controller.signal)
       .then((response) => {
-        if (!cancelled) {
+        if (!controller.signal.aborted) {
           setFlights(response);
           setLoading(false);
         }
       })
       .catch((err: ApiError) => {
-        if (!cancelled) {
-          setError(err);
-          setLoading(false);
-        }
+        // Ignore aborted requests — the user cancelled intentionally
+        if (controller.signal.aborted) return;
+        setError(err);
+        setLoading(false);
       });
 
     return () => {
-      cancelled = true;
+      controller.abort();
+      abortRef.current = null;
     };
   }, [
     client,
@@ -74,5 +95,5 @@ export function useScheduleSearch(
     refreshKey,
   ]);
 
-  return { flights, loading, error, refresh };
+  return { flights, loading, error, refresh, cancel };
 }
diff --git a/src/i18n/locales/de/common.json b/src/i18n/locales/de/common.json
index 542bd41b..b70ef46a 100644
--- a/src/i18n/locales/de/common.json
+++ b/src/i18n/locales/de/common.json
@@ -44,6 +44,9 @@
         "ESTIMATED-TIME-NOTE": "Arrival times and distances are estimated. Times may change depending on weather and airport load.",
         "FLIGHT-NOT-FOUND": "Flight not found.",
         "LOAD-FAILED": "Failed to load data. Please try again.",
+        "ERROR-TIMEOUT": "The server did not respond in time. Please try again.",
+        "ERROR-4XX": "Invalid search parameters. Please check your input and try again.",
+        "ERROR-5XX": "The server is temporarily unavailable. Please try again later.",
         "OPERATED-BY": "Operated by"
     },
     "BOARDING-STATUSES": {
diff --git a/src/i18n/locales/en/common.json b/src/i18n/locales/en/common.json
index 27c59774..d74ba65a 100644
--- a/src/i18n/locales/en/common.json
+++ b/src/i18n/locales/en/common.json
@@ -46,6 +46,9 @@
         "LOAD-FAILED": "Failed to load data. Please try again.",
         "LOAD-FAILED-TITLE": "Failed to load data",
         "LOAD-FAILED-MESSAGE": "API server is unavailable. Check your connection and try again.",
+        "ERROR-TIMEOUT": "The server did not respond in time. Please try again.",
+        "ERROR-4XX": "Invalid search parameters. Please check your input and try again.",
+        "ERROR-5XX": "The server is temporarily unavailable. Please try again later.",
         "OPERATED-BY": "Operated by"
     },
     "BREADCRUMBS": {
diff --git a/src/i18n/locales/es/common.json b/src/i18n/locales/es/common.json
index 74cab158..84396df7 100644
--- a/src/i18n/locales/es/common.json
+++ b/src/i18n/locales/es/common.json
@@ -44,6 +44,9 @@
         "ESTIMATED-TIME-NOTE": "Arrival times and distances are estimated. Times may change depending on weather and airport load.",
         "FLIGHT-NOT-FOUND": "Flight not found.",
         "LOAD-FAILED": "Failed to load data. Please try again.",
+        "ERROR-TIMEOUT": "The server did not respond in time. Please try again.",
+        "ERROR-4XX": "Invalid search parameters. Please check your input and try again.",
+        "ERROR-5XX": "The server is temporarily unavailable. Please try again later.",
         "OPERATED-BY": "Operated by"
     },
     "BOARDING-STATUSES": {
diff --git a/src/i18n/locales/fr/common.json b/src/i18n/locales/fr/common.json
index 1fbba4fe..db04583f 100644
--- a/src/i18n/locales/fr/common.json
+++ b/src/i18n/locales/fr/common.json
@@ -44,6 +44,9 @@
         "ESTIMATED-TIME-NOTE": "Arrival times and distances are estimated. Times may change depending on weather and airport load.",
         "FLIGHT-NOT-FOUND": "Flight not found.",
         "LOAD-FAILED": "Failed to load data. Please try again.",
+        "ERROR-TIMEOUT": "The server did not respond in time. Please try again.",
+        "ERROR-4XX": "Invalid search parameters. Please check your input and try again.",
+        "ERROR-5XX": "The server is temporarily unavailable. Please try again later.",
         "OPERATED-BY": "Operated by"
     },
     "BOARDING-STATUSES": {
diff --git a/src/i18n/locales/it/common.json b/src/i18n/locales/it/common.json
index fba7a1b6..6a67bef8 100644
--- a/src/i18n/locales/it/common.json
+++ b/src/i18n/locales/it/common.json
@@ -44,6 +44,9 @@
         "ESTIMATED-TIME-NOTE": "Arrival times and distances are estimated. Times may change depending on weather and airport load.",
         "FLIGHT-NOT-FOUND": "Flight not found.",
         "LOAD-FAILED": "Failed to load data. Please try again.",
+        "ERROR-TIMEOUT": "The server did not respond in time. Please try again.",
+        "ERROR-4XX": "Invalid search parameters. Please check your input and try again.",
+        "ERROR-5XX": "The server is temporarily unavailable. Please try again later.",
         "OPERATED-BY": "Operated by"
     },
     "BOARDING-STATUSES": {
diff --git a/src/i18n/locales/ja/common.json b/src/i18n/locales/ja/common.json
index 685fa118..5f789bdd 100644
--- a/src/i18n/locales/ja/common.json
+++ b/src/i18n/locales/ja/common.json
@@ -44,6 +44,9 @@
         "ESTIMATED-TIME-NOTE": "Arrival times and distances are estimated. Times may change depending on weather and airport load.",
         "FLIGHT-NOT-FOUND": "Flight not found.",
         "LOAD-FAILED": "Failed to load data. Please try again.",
+        "ERROR-TIMEOUT": "The server did not respond in time. Please try again.",
+        "ERROR-4XX": "Invalid search parameters. Please check your input and try again.",
+        "ERROR-5XX": "The server is temporarily unavailable. Please try again later.",
         "OPERATED-BY": "Operated by"
     },
     "BOARDING-STATUSES": {
diff --git a/src/i18n/locales/ko/common.json b/src/i18n/locales/ko/common.json
index 19d3928a..357c2c2a 100644
--- a/src/i18n/locales/ko/common.json
+++ b/src/i18n/locales/ko/common.json
@@ -44,6 +44,9 @@
         "ESTIMATED-TIME-NOTE": "Arrival times and distances are estimated. Times may change depending on weather and airport load.",
         "FLIGHT-NOT-FOUND": "Flight not found.",
         "LOAD-FAILED": "Failed to load data. Please try again.",
+        "ERROR-TIMEOUT": "The server did not respond in time. Please try again.",
+        "ERROR-4XX": "Invalid search parameters. Please check your input and try again.",
+        "ERROR-5XX": "The server is temporarily unavailable. Please try again later.",
         "OPERATED-BY": "Operated by"
     },
     "BOARDING-STATUSES": {
diff --git a/src/i18n/locales/ru/common.json b/src/i18n/locales/ru/common.json
index 6b129826..c5509bbf 100644
--- a/src/i18n/locales/ru/common.json
+++ b/src/i18n/locales/ru/common.json
@@ -46,6 +46,9 @@
         "LOAD-FAILED": "Не удалось загрузить данные. Попробуйте снова.",
         "LOAD-FAILED-TITLE": "Не удалось загрузить данные",
         "LOAD-FAILED-MESSAGE": "API сервер недоступен. Проверьте подключение и попробуйте снова.",
+        "ERROR-TIMEOUT": "Время ожидания ответа от сервера истекло. Попробуйте снова.",
+        "ERROR-4XX": "Неверные параметры поиска. Проверьте введённые данные и попробуйте снова.",
+        "ERROR-5XX": "Сервер временно недоступен. Пожалуйста, повторите попытку позже.",
         "OPERATED-BY": "Выполняет рейс"
     },
     "BREADCRUMBS": {
diff --git a/src/i18n/locales/zh/common.json b/src/i18n/locales/zh/common.json
index e9cfea3c..126d25d2 100644
--- a/src/i18n/locales/zh/common.json
+++ b/src/i18n/locales/zh/common.json
@@ -44,6 +44,9 @@
         "ESTIMATED-TIME-NOTE": "Arrival times and distances are estimated. Times may change depending on weather and airport load.",
         "FLIGHT-NOT-FOUND": "Flight not found.",
         "LOAD-FAILED": "Failed to load data. Please try again.",
+        "ERROR-TIMEOUT": "The server did not respond in time. Please try again.",
+        "ERROR-4XX": "Invalid search parameters. Please check your input and try again.",
+        "ERROR-5XX": "The server is temporarily unavailable. Please try again later.",
         "OPERATED-BY": "Operated by"
     },
     "BOARDING-STATUSES": {
diff --git a/src/shared/api/client.ts b/src/shared/api/client.ts
index 05644416..76308804 100644
--- a/src/shared/api/client.ts
+++ b/src/shared/api/client.ts
@@ -58,18 +58,19 @@ export class ApiClient {
   async get<T>(
     path: string,
     query?: Record<string, string | number | boolean>,
+    signal?: AbortSignal,
   ): Promise<T> {
     const url = this.buildUrl(path, query);
-    return this.executeWithRetry<T>(url, { method: "GET" });
+    return this.executeWithRetry<T>(url, { method: "GET" }, signal);
   }
 
-  async post<T>(path: string, body: unknown): Promise<T> {
+  async post<T>(path: string, body: unknown, signal?: AbortSignal): Promise<T> {
     const url = this.buildUrl(path);
     return this.executeWithRetry<T>(url, {
       method: "POST",
       body: JSON.stringify(body),
       headers: { "Content-Type": "application/json" },
-    });
+    }, signal);
   }
 
   private buildUrl(
@@ -89,6 +90,7 @@ export class ApiClient {
   private async executeWithRetry<T>(
     url: string,
     init: RequestInit,
+    externalSignal?: AbortSignal,
   ): Promise<T> {
     const headers = new Headers(init.headers ?? {});
     headers.set("Accept-Language", this.locale);
@@ -106,11 +108,16 @@ export class ApiClient {
         }
       }
 
+      // Abort immediately if the external signal fired before we started.
+      if (externalSignal?.aborted) {
+        throw new ApiNetworkError(new Error("Aborted"));
+      }
+
       try {
         const response = await this.fetchWithTimeout(url, {
           ...init,
           headers,
-        });
+        }, externalSignal);
 
         if (response.ok) {
           return (await response.json()) as T;
@@ -150,6 +157,11 @@ export class ApiClient {
           throw err;
         }
         if (err instanceof Error) {
+          // External cancellation — don't retry, re-throw as-is so the
+          // caller can distinguish "user cancelled" from "network error".
+          if (err.name === "AbortError" || (externalSignal?.aborted)) {
+            throw new ApiNetworkError(err);
+          }
           if (attempt < this.maxRetries) {
             lastError = new ApiNetworkError(err);
             continue;
@@ -166,10 +178,19 @@ export class ApiClient {
   private async fetchWithTimeout(
     url: string,
     init: RequestInit,
+    externalSignal?: AbortSignal,
   ): Promise<Response> {
     const controller = new AbortController();
     const timeoutId = setTimeout(() => controller.abort(), this.timeoutMs);
 
+    // Forward external cancellation (e.g. user clicks "Отменить поиск")
+    // to the internal controller so the fetch is actually aborted.
+    let externalListener: (() => void) | undefined;
+    if (externalSignal) {
+      externalListener = () => controller.abort();
+      externalSignal.addEventListener("abort", externalListener);
+    }
+
     try {
       return await this.fetchFn(url, {
         ...init,
@@ -177,11 +198,18 @@ export class ApiClient {
       });
     } catch (err) {
       if (err instanceof Error && err.name === "AbortError") {
+        // Distinguish user cancellation from timeout.
+        if (externalSignal?.aborted) {
+          throw err; // Let the caller handle it as a cancellation.
+        }
         throw new ApiTimeoutError(this.timeoutMs);
       }
       throw err;
     } finally {
       clearTimeout(timeoutId);
+      if (externalSignal && externalListener) {
+        externalSignal.removeEventListener("abort", externalListener);
+      }
     }
   }