Behind Enemy Lines is an add-on for Microsoft Combat Flight Simulator: WWII Europe Series. This package contains thirty missions, fifteen each for the Royal Air Force and the Luftwaffe, which are set around fictional events leading up to the D-Day landings. The missions are varied. Some of the Allied missions either start or end on a carrier. There are sorties to both attack enemy airfields and defend ships and airfields against attack. On the Luftwaffe side the missions are in many ways the opposite of the RAF missions, attack carriers, intercept bombers etc. Both sides have missions based around a spy called Solitaire with the Luftwaffe trying to prevent his/her escape and the RAF attempting to facilitate it.