What is the flag carrier of London?

Answer 1

A flag carrier is a transportation company, such as an airline or shipping company, that, being locally registered in a given state, enjoys preferential rights or privileges accorded by the government for international operations. The term also refers to any carrier that is or was owned by a government,[1] even long after their privatization.[2]

Flag carriers may be known as such due to maritime law requiring all aircraft or ships to display the state flag of the country of their registry.[3]

A flag carrier (if it is a certificated airline rather than a holding company, conglomerate, or multinational private equity firm) may also be known as a national airline or a national carrier, although this can have different legal meanings in some countries.