diff --git a/src/i18n/resolver.test.ts b/src/i18n/resolver.test.ts
index f47f9910..2c0fcf0f 100644
--- a/src/i18n/resolver.test.ts
+++ b/src/i18n/resolver.test.ts
@@ -33,13 +33,13 @@ describe("isLanguage", () => {
 describe("resolveLocaleFromPath", () => {
   it("extracts BCP-47 locale from the first path segment", () => {
     expect(resolveLocaleFromPath("/ru-ru/onlineboard")).toBe("ru-ru");
-    expect(resolveLocaleFromPath("/en-us/onlineboard/flight/SU100")).toBe("en-us");
+    expect(resolveLocaleFromPath("/en-en/onlineboard/flight/SU100")).toBe("en-en");
     expect(resolveLocaleFromPath("/de-de/schedule")).toBe("de-de");
   });
 
   it("auto-promotes a bare short language code to its BCP-47 cousin", () => {
     expect(resolveLocaleFromPath("/ru/onlineboard")).toBe("ru-ru");
-    expect(resolveLocaleFromPath("/en/onlineboard/flight/SU100")).toBe("en-us");
+    expect(resolveLocaleFromPath("/en/onlineboard/flight/SU100")).toBe("en-en");
     expect(resolveLocaleFromPath("/de/schedule")).toBe("de-de");
   });
 
@@ -63,8 +63,8 @@ describe("stripLocaleFromPath", () => {
       locale: "ru-ru",
       rest: "/onlineboard",
     });
-    expect(stripLocaleFromPath("/en-us/onlineboard/flight/SU100")).toEqual({
-      locale: "en-us",
+    expect(stripLocaleFromPath("/en-en/onlineboard/flight/SU100")).toEqual({
+      locale: "en-en",
       rest: "/onlineboard/flight/SU100",
     });
   });
diff --git a/src/i18n/resolver.ts b/src/i18n/resolver.ts
index 105385b2..498c06e0 100644
--- a/src/i18n/resolver.ts
+++ b/src/i18n/resolver.ts
@@ -3,7 +3,7 @@
  * file lookup, API path segment, and `Accept-Language` header.
  *
  * Mirrors Angular's `LocalizationService`: URL is BCP-47 (`/ru-ru/`,
- * `/en-us/`, `/zh-cn/`...), backend + translation files use the short
+ * `/en-en/`, `/zh-zh/`...), backend + translation files use the short
  * 2-letter language part only (`ru`, `en`, `zh`...). This split keeps
  * the customer's URL contract while reusing a single set of locale
  * resources.
@@ -13,13 +13,13 @@ export type Language = "ru" | "en" | "es" | "fr" | "it" | "ja" | "ko" | "zh" | "
 
 export type LocaleCode =
   | "ru-ru"
-  | "en-us"
+  | "en-en"
   | "es-es"
   | "fr-fr"
   | "it-it"
-  | "ja-jp"
-  | "ko-kr"
-  | "zh-cn"
+  | "ja-ja"
+  | "ko-ko"
+  | "zh-zh"
   | "de-de";
 
 export const LANGUAGES: readonly Language[] = [
@@ -27,7 +27,7 @@ export const LANGUAGES: readonly Language[] = [
 ] as const;
 
 export const LOCALE_CODES: readonly LocaleCode[] = [
-  "ru-ru", "en-us", "es-es", "fr-fr", "it-it", "ja-jp", "ko-kr", "zh-cn", "de-de",
+  "ru-ru", "en-en", "es-es", "fr-fr", "it-it", "ja-ja", "ko-ko", "zh-zh", "de-de",
 ] as const;
 
 export const DEFAULT_LOCALE_CODE: LocaleCode = "ru-ru";
@@ -36,15 +36,20 @@ export const DEFAULT_LANGUAGE: Language = "ru";
 const languageSet: ReadonlySet<string> = new Set(LANGUAGES);
 const localeCodeSet: ReadonlySet<string> = new Set(LOCALE_CODES);
 
+// Angular's URL contract is `/{country}-{language}` where the two
+// halves repeat the same 2-letter language code (see
+// `ClientApp/src/app/shared/services/localization.service.ts` —
+// `Country = baseHref[1..3]`, `Language = baseHref[4..6]`). We mirror
+// that exact shape so the React MF remote shares Angular's URL surface.
 const LANGUAGE_TO_LOCALE_CODE: Record<Language, LocaleCode> = {
   ru: "ru-ru",
-  en: "en-us",
+  en: "en-en",
   es: "es-es",
   fr: "fr-fr",
   it: "it-it",
-  ja: "ja-jp",
-  ko: "ko-kr",
-  zh: "zh-cn",
+  ja: "ja-ja",
+  ko: "ko-ko",
+  zh: "zh-zh",
   de: "de-de",
 };
 
@@ -58,7 +63,7 @@ export function isLocaleCode(x: string): x is LocaleCode {
 
 /**
  * Extract the language part from a BCP-47 locale code.
- * `localeToLanguage("en-us")` → `"en"`.
+ * `localeToLanguage("en-en")` → `"en"`.
  */
 export function localeToLanguage(code: LocaleCode): Language {
   return code.slice(0, 2) as Language;
@@ -66,7 +71,7 @@ export function localeToLanguage(code: LocaleCode): Language {
 
 /**
  * Promote a short language code to its canonical URL locale code.
- * `languageToLocale("en")` → `"en-us"`. Used when the URL needs the
+ * `languageToLocale("en")` → `"en-en"`. Used when the URL needs the
  * BCP-47 form but only the short language is in hand.
  */
 export function languageToLocale(lang: Language): LocaleCode {
diff --git a/src/i18n/useLocale.ts b/src/i18n/useLocale.ts
index 7d282b15..3f459829 100644
--- a/src/i18n/useLocale.ts
+++ b/src/i18n/useLocale.ts
@@ -2,7 +2,7 @@
  * `useLocale()` — central hook that resolves the current page's
  * locale from `useParams<{lang}>` and exposes both forms:
  *
- *   - `locale`    — BCP-47 URL code (`"ru-ru"`, `"en-us"`, …) for
+ *   - `locale`    — BCP-47 URL code (`"ru-ru"`, `"en-en"`, …) for
  *                   building outgoing links and reading from
  *                   `window.location`.
  *   - `language`  — short code (`"ru"`, `"en"`, …) for the i18n file
diff --git a/src/routes/[lang]/layout.tsx b/src/routes/[lang]/layout.tsx
index 3e1cf2e7..9da80f97 100644
--- a/src/routes/[lang]/layout.tsx
+++ b/src/routes/[lang]/layout.tsx
@@ -15,12 +15,12 @@ import type i18next from "i18next";
 
 // Register all PrimeReact locales once at module load. The active
 // locale is selected per-render via setPrimeLocale() so that switching
-// between /ru-ru and /en-us swaps Calendar/AutoComplete labels too.
+// between /ru-ru and /en-en swaps Calendar/AutoComplete labels too.
 registerPrimeLocales(addLocale);
 
 /**
  * Locale-scoped layout. Validates the `lang` URL segment (BCP-47:
- * `ru-ru`, `en-us`, …; legacy short codes like `ru` are auto-promoted
+ * `ru-ru`, `en-en`, …; legacy short codes like `ru` are auto-promoted
  * to their canonical BCP-47 cousin), creates an i18n instance for
  * the matching language file, and updates the shared ApiClient's
  * locale so backend responses come back in the right language.
@@ -64,7 +64,7 @@ export default function LangLayout(): JSX.Element {
     return (
       <div>
         <h2>404 — Unknown locale: {rawLang}</h2>
-        <p>Supported: ru-ru, en-us, es-es, fr-fr, it-it, ja-jp, ko-kr, zh-cn, de-de</p>
+        <p>Supported: ru-ru, en-en, es-es, fr-fr, it-it, ja-ja, ko-ko, zh-zh, de-de</p>
       </div>
     );
   }
diff --git a/src/shared/seo/hreflang.test.ts b/src/shared/seo/hreflang.test.ts
index 60078ed0..ade33d8c 100644
--- a/src/shared/seo/hreflang.test.ts
+++ b/src/shared/seo/hreflang.test.ts
@@ -43,10 +43,10 @@ describe("buildHreflangSet", () => {
     });
 
     const en = result.find((entry) => entry.lang === "en");
-    expect(en?.href).toBe("https://www.aeroflot.ru/en-us/onlineboard");
+    expect(en?.href).toBe("https://www.aeroflot.ru/en-en/onlineboard");
 
     const ja = result.find((entry) => entry.lang === "ja");
-    expect(ja?.href).toBe("https://www.aeroflot.ru/ja-jp/onlineboard");
+    expect(ja?.href).toBe("https://www.aeroflot.ru/ja-ja/onlineboard");
   });
 
   it("preserves paths with nested segments", () => {
diff --git a/src/shared/seo/hreflang.ts b/src/shared/seo/hreflang.ts
index 45a80ca5..1ffcf1c5 100644
--- a/src/shared/seo/hreflang.ts
+++ b/src/shared/seo/hreflang.ts
@@ -16,7 +16,7 @@ export interface HreflangEntry {
  * Returns 9 language entries + 1 x-default entry (pointing to the
  * default language). Hreflang attribute uses the short language code
  * (`hreflang="en"`); the URL itself uses the BCP-47 locale code
- * (`/en-us/...`) to match the customer's URL contract.
+ * (`/en-en/...`) to match the customer's URL contract.
  */
 export function buildHreflangSet(args: {
   canonicalOrigin: string;