diff --git a/src/features/online-board/types.test.ts b/src/features/online-board/types.test.ts
index 7a39d74f..69bbf881 100644
--- a/src/features/online-board/types.test.ts
+++ b/src/features/online-board/types.test.ts
@@ -22,6 +22,7 @@ import type {
   IAircraftInfo,
   IEquipmentFull,
   IDaysOfWeek,
+  IDuration,
 } from "./types.js";
 
 /**
@@ -301,4 +302,21 @@ describe("online-board types extension", () => {
     };
     expect(leg.daysOfWeek?.flight).toBe("1111111");
   });
+
+  it("IDuration has days/hours/minutes and optional isNegative", () => {
+    const d: IDuration = { days: 0, hours: 1, minutes: 30, isNegative: true };
+    expect(d.days).toBe(0);
+    expect(d.hours).toBe(1);
+    expect(d.minutes).toBe(30);
+    expect(d.isNegative).toBe(true);
+  });
+
+  it("IFlightLeg accepts optional estimatedDuration and scheduledDuration", () => {
+    const leg: Partial<IFlightLeg> = {
+      estimatedDuration: { days: 0, hours: 1, minutes: 30 },
+      scheduledDuration: { days: 0, hours: 1, minutes: 45 },
+    };
+    expect(leg.estimatedDuration?.hours).toBe(1);
+    expect(leg.scheduledDuration?.minutes).toBe(45);
+  });
 });
diff --git a/src/features/online-board/types.ts b/src/features/online-board/types.ts
index 4d0b7bc8..d58c9812 100644
--- a/src/features/online-board/types.ts
+++ b/src/features/online-board/types.ts
@@ -113,6 +113,21 @@ export interface IDaysOfWeek {
   flight: string;
 }
 
+// ---------------------------------------------------------------------------
+// Duration
+// ---------------------------------------------------------------------------
+
+/**
+ * Structured duration for flight timings. `isNegative` flags an uncertain
+ * or "specifying" state (estimated arrival is earlier than departure).
+ */
+export interface IDuration {
+  days: number;
+  hours: number;
+  minutes: number;
+  isNegative?: boolean;
+}
+
 // ---------------------------------------------------------------------------
 // Transition (registration/boarding/deboarding)
 // ---------------------------------------------------------------------------
@@ -180,6 +195,8 @@ export interface IFlightLeg {
   updated: string;
   transition?: IFlightTransitions;
   daysOfWeek?: IDaysOfWeek;
+  estimatedDuration?: IDuration;
+  scheduledDuration?: IDuration;
 }
 
 // ---------------------------------------------------------------------------