You should copy what AirTraffic Controller or whatever that game is on the iTouch did, basically have each runway a different colour, and then have each plane the colour of the runway it needs to land on.

Also, the control scheme is pretty difficult. What the iTouch game did was sort of drawing mechanism, where you draw the path the plane needed to take, and it would automatically lock on to the runway. It's hard to land planes the first time in your game, maybe make the plane snap on to the runway a bit better?

Good game though!

P.