planes were ordered to make their rendezvous over Yakushima at due to weather conditions over Iwo Jima (the Hiroshima mission rendezvous). That same morning, on the day of the mission, the ground crew notified Sweeney that a faulty fuel transfer pump made it impossible to utilize some of fuel in the tail, but Sweeney, as aircraft commander, elected to proceed with the mission. Before takeoff, Tibbets warned Sweeney that he had lost at least 45 minutes of flying time because of the fuel pump problem, and to take no more than fifteen minutes at the rendezvous before proceeding directly to the primary target. After takeoff from Tinian, Bockscar reached its rendezvous point and after circling for an extended period, found The Great Artiste, but not The Big Stink. Climbing to 30,000 feet, the assigned rendezvous altitude, both aircraft slowly circled Yakushima Island. Though Sweeney had been ordered not to wait at the rendezvous for the other aircraft longer than fifteen minutes before proceeding to the primary target, Sweeney continued to wait for The Big Stink, perhaps at the urging of Commander Frederick Ashworth, the plane's weaponeer. After exceeding the original rendezvous time limit by a half-hour, Bockscar, accompanied by The Great Artiste, proceeded to the primary target, Kokura. No fewer than three bomb runs were made, but the delay at the rendezvous had resulted in 7/10ths cloud cover over the primary target, and the bombardier was unable to drop. By the time of the third bomb run, Japanese antiaircraft fire was getting close, and Japanese fighter planes could be seen climbing to intercept Bockscar. Poor bombing visibility and an increasingly critical fuel shortage eventually forced Bockscar to divert from Kokura and attack the secondary target, Nagasaki. As they approached Nagasaki, the heart of the city's downtown was covered by dense cloud, and Sweeney and Ashworth, initially decided to bomb Nagasaki using radar. However, a small opening in the clouds allowed Bockscar's bombardier to verify the target as Nagasaki. As the crew had been ordered to drop the bomb visually if possible, Sweeney decided to proceed with a visual bomb run. Bockscar then dropped Fat Man, with a blast yield equivalent to 21 kilotons of TNT. It exploded 43 seconds later at above the ground, at least northwest of the planned aim point. The failure to drop Fat Man at the precise bomb aim point caused the atomic blast to be