Hi,
This is a fantastic game and I really love playing it! I think that it could be even better if you added challenges for each type of aircraft, like glider races, journeys and difficult and easy landings for airliners, and aerobatic challenges for stunt planes. Each time the player completes a challenge, I think they should be awarded a medal or mark for how well they did it, which can then go down as a gamecentre achievement. Thanks!
Tristan