what folder should I put the flight plans in?

C:\Documents and Settings\(your name)\My Documents\Flight simulator X FilesThat's where my flight plans are.Tony

The .FLT file should be in the same folder as the mission. Example: The AustrianSoaring.FLT is in C:\Program Files\Microsoft Games\Microsoft Flight Simulator X\Missions\Just for Fun\AustrianSoaring