What is the meaning of Flag_carrier?

A person carrying a standard or flag, usually at sporting events and parades, previously on the battlefield.

A transportation company, such as a shipping or airline company, that is registered in a given state.

A strong supporter of a cause, or perhaps the strongest and most visible supporter of said cause.

A national airline (typically having the flag, or other national insignia, on the tail).

An aircraft carrier serving as a flagship.

Source: wiktionary.org