This is when pilots would learn the theoretical aspects of flying a plane during a war. Trainees would have gone to an initial training school before coming to No. 24 EFTS, so they would know some of the technicalities behind flying, but there is much more to military aviation than just flying the plane. Ground school would cover things like navigation, repair, aircraft recognition, administration, and the mechanics of both the plane and its weapons. According to the trainee souvenir booklets, the most difficult class tended to be navigation. Charting courses needed complex math and a good mental image of the area.