The Schweinfurt–Regensburg mission was an air combat battle in World War II. A strategic bombing attack flown by B-17 Flying Fortresses of the U.S. Army Air Forces on August 17, 1943, it was conceived as an ambitious plan to cripple the German aircraft industry. The mission was also known as the ""double-strike mission"" because it entailed two large forces of bombers attacking separate targets in order to disperse fighter reaction by the Luftwaffe, and was the first ""shuttle"" mission, in which all or part of a mission landed at a different field and later bombed another target returning to its base.After being postponed several times by unfavorable weather, the operation, known within the Eighth Air Force as ""Mission No. 84"", was flown on the anniversary of the first daylight raid by the Eighth Air Force. Mission No. 84 was a strike by 376 bombers of sixteen bomb groups against German heavy industry well beyond the range of escorting fighters. The mission inflicted heavy damage on the Regensburg target, but at catastrophic loss to the force, with 60 bombers lost and many more damaged beyond economical repair. As a result, the Eighth Air Force was unable to follow up immediately with a second attack that might have seriously crippled German industry. When Schweinfurt was finally attacked again two months later, the lack of long-range fighter escort had still not been addressed and losses were even higher. As a consequence, deep penetration strategic bombing was curtailed for five months.