flag carrier

Wiktionary

1. n. A person carrying a standard or flag, usually at sporting events and parades, previously on the battlefield.
2. n. business A transportation company, such as a shipping or airline company, that is registered in a given state
3. n. politics A strong supporter of a cause, or perhaps the strongest and most visible supporter of said cause.
4. n. A national airline (typically having the flag, or other national insignia, on the tail)
5. n. military, nautical An aircraft carrier serving as a flagship