Boeing Field, Seattle, Washington State. The first XB-29, the prototype of the B-29, takes flight. It was the first aircraft with a pressurized cabin, and many future aircraft, particularly passenger aircraft, would be modeled after it. The B-29 project would become the most expensive of the entire war, costing nearly 50% more than the Manhattan Project. In today’s terms, the aircraft, from design to completion, cost the equivalent of $55.6 billion.
