What do you mean, fly together?

In modern Chinese, flying in pairs means:

1. Double flights refer to round-trip air tickets or double air tickets.

This is a common phrase in travel. Double flight means that both round trips are by plane.

Extended material: two people travel and travel are one language. Two-way flight means that the round-trip traffic is all planes. There is also a saying that it is like flying solo, which means there is only one flight. Similar nouns include "two-bedroom" (round-trip train sleeper) and "single room" (a plane and a train sleeper). ?

For example, a three-day trip from Shanghai to Wuyuan means flying from Shanghai to Wuyuan (Jingdezhen) and then flying back to Shanghai from Wuyuan. Double flight means that during the journey, both the journey and the return journey are planes, so it is called double flight.

References:

Baidu encyclopedia-travel double flight