1#, 2# and 3# take off at the same time, and when it reaches 1/8 laps (1#, 2# and 3# each consume 1/4 boxes), 1# will fill up the 2# and 3# fuel tanks.

2# and 3# keep going 1/8 laps. When they reach 1/4 laps (2# and 3# each consume 1/4 boxes), 2# fills up the 3# fuel tank and the remaining 1/2 boxes fly back to the starting point;

3# is full, you can continue to move forward 1/2 laps to 3/4 laps;

At this time, the remaining 1/4 laps can return to the starting point, just like the original 1/4 laps, it takes 2 sorties to meet.