I suggest doing this achievement along side with Danger Zone and No Fly Zone. A good tip for this is have your sound turned up because when your planes are about to collide it beeps. Also watch for the red circles that appear around your planes when they are getting close. Make sure to keep avoiding crashing without landing planes. By the time 15 planes are up, 2 minutes should have passed and now all you have to do is make 3 separate pairs crash. They do not have to be at the same exact same time you have about a second after the first collision to make sure the others crash. This should not be to difficult due to the amount of planes on the screen.