The U.S. built and flew a few disc aircraft during WW2. The Chance Vought V-173
first flew 23 November 1942, which had excellent STOL capabilities and was
apparently impossible to stall. The Navy ordered two XF5U-1 which didn't get
their propellers until 1947 and were not proceded with since the Navy decided
jets were the way to go.

This brings 2 questions to mind.

1) if jets hadn't been successful that early would the aircraft have found a
militarily justifiable purpuse?

2) as thin as the saucer was what kind of useful payload could be expected?

Dan, U.S. Air Force, retired