The bomb parts were transported by plane and ship. They were mostly assembled on Tinian before being loaded onto Enola Gay (Hiroshima) and Bock's Car (Kokura and Nagasaki). To avoid an accidental nuclear detonation on Tinian in a plane crash, the bombs were not (fully) assembled until the B-29s were well away from the island. Then, weaponeer Deke Parsons crawled into the bomb bay to put the (small) finishing touches on the device.

Several parts of the gun-type Little Boy device, including the uranium "bullet," were sent by sea. The heavy cruiser USS Indianapolis left California on July 16th and arrived at Tinian ten days later. The metal box containing the bomb parts was welded to the deck of a cabin and watched over 24 hours a day by its escort of officers and men.

The uranium "target," wasn't ready until July 24th, so it had to be flown by plane. C-54 transports delivered it on the 30th.

All of Fat Man's parts were delivered by air. A C-54 and three B-29s delivered the plutonium core and the explosives for the bomb from Kirtland Air Force Base in New Mexico to Tinian in late July.

E: changes for clarity.