Premise: The Messerschmitt Me 263 "Scholle" (plaice) was a rocket-powered fighter aircraft developed from the Me 163 "Komet" towards the end of World War II. Three prototypes were built but never flown under their own power as the rapidly deteriorating military situation in Germany prevented the completion of the test program.
Hypothesis: Three prototypes of a fighter plane were never flown towards the end of WW II because Germany was fast losing the war and this prevented the test program from being completed.