fly the flag

English

fly the flag (third-person singular simple present flies the flag, present participle flying the flag, simple past flew the flag, past participle flown the flag)

To be registered in a particular country and display that country's flag as a result. (of a ship, airline etc)
(idiomatic) To support one's country enthusiastically.
- 2017 March 14, Stuart James, “Leicester stun Sevilla to reach last eight after Kasper Schmeichel save”, in the Guardian‎^[1]:
  Now they are the English champions, flying the flag for their country in Europe’s premier club competition and managed by a 53‑year‑old who only got the job on Sunday night.