The most expensive American weapons program of World War II was not the Manhattan Project at $1.9 billion. It was the $3 billion Boeing B-29 Superfortress, roughly $54 billion today, the machine built to drop the bomb. This episode tells the biography of an aircraft ordered by the hundreds before its prototype had flown, built in four factories in Washington, Kansas, Georgia, and Nebraska, whose engines were practically guaranteed to catch fire on takeoff, and which reshaped global warfare anyway.

From the 1940 specification demanding 20,000 pounds of bombs over 2,667 miles at 400 mph, through the February 1943 crash that killed test pilot Edmund T. Allen and his crew in a Seattle meatpacking plant, and the ‘Battle of Kansas’ where mechanics modified 150 aircraft outdoors in winter snow in five weeks, the story follows the B-29 to the Marianas, the 200-mph jet stream that defeated its analog computers, Curtis LeMay’s stripped-down low-altitude firebombing and Operation Starvation mining, the Silverplate atomic bombers Enola Gay and Bockscar, and Stalin’s rivet-for-rivet Tupolev Tu-4 copy of three interned aircraft.

• Why pilots had to dive or fly flat after takeoff to cool the Wright R-3350 engines, with top cylinders replaced every 25 flight hours and whole engines every 75
• Thermal creep in 1,500-degree turbosupercharger blades, solved by Dr. Sanford Moss with Vitallium, a cobalt-chromium-molybdenum alloy invented in 1932 for dentures and cast by the lost-wax method the Axis could not copy
• The first pressurized production bomber, the two-foot crawl tube over the bomb bays, and the General Electric central fire control system with gear-driven analog computers directing remote turrets
• Operation Matterhorn and flying fuel over the Hump versus the 1,500-mile path to Tokyo from Saipan, Tinian, and Guam
• Reversible-pitch propellers that saved Bockscar at Okinawa, why the Lancaster was rejected, and the metric nightmare of copying 1/16-inch aluminum skin in Soviet factories