Birth of the B-29 was a 1945 propaganda film commissioned by the US War Department. As the name implies, it concerned the production of the B-29 bomber and its use in the aerial bombing of Japan in World War II.

Opening amid scenes of volcanic eruption, the narrator begins a brief description of the Japanese, and their warlike nature, mentioning such concepts as bushido, Hakko ichiu, and Shinto, with the narrator informs us is the belief that everything comes from the sky. The latter point will prove correct, because the Americans are building a devastating new weapon that will be able to travel vast distances and drop giant payloads of bombs on the Japanese mainland, the B-29 super fortress.

The creation and assembling of the super fortress in giant factories is then chronicled as Americans from every walk of life, black, white, male and female, work together to assemble the giant airplanes, each one of which is larger than the Mayflower. The creation of the bomber is the product of all of their work, as well as the work of the miners and lumberjacks who supplied the raw material, the people who bought war bonds, and the servicemen who died so that the workers could have the time to build it.

Soon the XXth Air Force is created and the planes are flown to China, where the Americans' allies are happy to build airfields to help defeat the common enemy. The film ends with a B-29 taking off and the narrator saying "Next stop - Japan!"