What does traveling together mean?

Double-fly travel means that both the outbound and return journeys are by plane.

Tourism and flying together are common terms in tourism. Double flight means that both round-trip transportation are by plane. There are also terms such as flying solo, which means that only one trip is by air. Similar terms include "double sleeper" (a sleeper train for both flights) and "single sleeper" (a sleeper train for one flight).

For example, there is a tourist route that is a three-day two-flight tour from Shanghai to Wuyuan. That means you take a flight from Shanghai to Wuyuan (Jingdezhen), and then take a flight from Wuyuan back to Shanghai after the tour. Double flight means that during the journey, both the outbound and return journeys are by air, so it is called double flight. It has nothing to do with the number of people.

Extended information:

In addition to double flights, there are other modes of transportation.

Flying alone and sleeping alone means one journey by plane and one journey by train. Maybe the outbound journey is a flight and the return journey is by train. On the contrary, the outbound journey is by train and return by plane. Generally speaking, it is the outbound train and the return journey by plane. This is because it is more user-friendly to consider that guests are tired after traveling and take a plane back. Other modes of transportation cannot reach the destination directly and require transfers, so there are three flights with one sleeper, two flights with two sleepers, four flights, four sleepers, etc.

Of course, the distance to the tourist destination and transportation time must also be considered. For example, if the Hainan tourist route says double flight, it means taking a plane from Beijing to Hainan, and then flying back to Beijing after the trip. The same is true for trains, and the same is true for solo flights and sleeping accommodation.

Baidu Encyclopedia - Traveling together