For the length of the Occupation of Japan, from defeat in 1945 to the return of sovereignty in 1952, the skies belonged to the Allies.
Among the less well-known punitive measures implemented by Gen. Douglas MacArthur and the American GHQ from their roost in the Daiichi Seimei Building in Marunouchi was a complete ban on Japanese civil, and of course military, aviation, as well as airplane research, development and manufacturing of any kind.
Though it was just one of a long list of humiliating prohibitions that was part and parcel of Japan's complete and unconditional surrender, the aviation ban must have been particularly painful.