What was the Army Air Corps and how was it different from the U.S. Air Force?
Essentially they were the same thing known by different names at different times. According to the Army Air Forces Historical Assn., the present-day U.S. Air Force previously had several other names.
It came into being in 1907 as the Aeronautical Section of the Army Signal Corps.
In 1914, the name was changed to Aviation Section (Signal Corps). In 1918, the official name became the United States Army Air Service.
Then, in 1926, it became the United States Army Air Corps. In 1941, the corps became the United States Army Air Forces. And finally, in 1947, it became the United States Air Force.