I think Ouch had the right idea also. I have also had this problem before. What I attribute it to was "colliding" with the default enemy plane the game puts up because it has not got the information on the friendly plane from the server yet.
The way I fixed the problem was NEVER launching until the Roster has listed EVERY pilot playing. In other words, I would make note of the # of players in the arena when I come in, then go to the roster and continue hitting "Refresh" until the numbers of each country stop updating. If the numbers for the three countries add up to the number of players in the game, then all information on server should be updated on your computer. There should be no more default ponies flying around and it should be safe to launch. Since I have adopted this update process, I have not had any problems blowing up on runway since. Although it was VERY frustrating trying to figure out why.