FS9 loading last used a/c: even if new one chosen

Hello everyone. Im hoping someone on here can shed some light on this problem Im experiencing. Its best illustrated through example:-----------------------------------------------------I start FS9 and do a flight in a Posky A340.I then exit the sim and come back to it later. I set up a flight in a Twin Otter and then hit the "Fly!" button.The Posky A340 loads :(-----------------------------------------------------I can only have the Twin Otter load if I exit & re-start the sim.Why would FS9 be "remembering" the last used plane and loading that instead of the other airplane I've chosen?Woudl be real grateful if any of you have a fix or advice on this matter! Thanks very much :)