You can go have a shot or two of your favorite vodka while you fly to the ships. Once you land kill 6 guys. Stand on the first boat and use your fire bomb from there to get all three ships.
Simply put:
- you do not need to be flying to use the flame oil.
- you can get all three ships from the ground when standing on the first boat.
Useless I know but I am sure at least once you flew and had a brain fart forgetting to burn the ships.