the Schweinfurt force would be left to face the full fury of the Luftwaffe on its return to England. The plan was brutally simple: LeMay would fight his way in and Williams would fight his way out." Weather delays Eighth Air Force bomber operations were calculated with one to two hours of climb and assembly into formations factored into mission lengths. In addition the mission length for the Regensburg force was anticipated to be of eleven hours' duration, so that commanders had only a 90-minute "window" in which to launch the mission and still allow the 4th Bombardment Wing B-17s to reach North Africa in daylight. Mission 84 planning indicated a takeoff window from dawn (approximately 06:30 British Double Summer Time) to approximately 08:00 without cancelling the mission. At dawn of August 17, after airmen had gone to their airplanes, England was covered in fog. The mission takeoff was delayed until 08:00, when the fog had cleared sufficiently over East Anglia to allow the 4th Bombardment Wing to take off using instruments, a technique they had practiced. Although attacking both targets simultaneously was deemed critical to success of the mission without prohibitive loss, the Regensburg force was ordered to take off, even though the 1st Bombardment Wing remained grounded at its bases by the adverse weather. By the time the fog had sufficiently cleared over the Midlands, the Regensburg force had already reached the coast of the Netherlands, which indicated that reacting German fighters would have sufficient time to land, replenish, and attack the second task force. Consequently, the launch of the Schweinfurt force was further delayed to allow U.S. escort fighters sufficient time to return to base to rearm for a second escort mission. In all the 1st Wing was delayed more than three hours behind the 4th Wing. Regensburg strike force The Regensburg task force was led by the 4th Bombardment Wing commander, Colonel Curtis E. LeMay. This mission would make LeMay's name as a combat leader. The task force consisted of seven B-17 Groups totalling 146 aircraft, each group but one flying a 21-aircraft combat box tactical formation. The groups were organized into three larger formations termed "provisional combat wings", three groups in a Vee formation wing box leading the procession, followed in trail by two wing boxes of two groups each in echelon formation with one group leading and the second trailing at lower altitude. Approximately