After Franklin D. Roosevelt returned from his meeting with British Prime Minister Winston Churchill in Casablanca in January 1943, Hap Arnold knew something had to change.Arnold, the legendary general who led the U.S. Army Air Forces during World War II, didn’t like that FDR flew to Morocco on a civilian plane. Believing it was the military’s job to transport the commander in chief, he ordered that a transport version of the B-24 bomber be conve…