Assertion: ufo | /r/HasProperty | aircraft
Facets:
Source sentences:
text: It was then revised again to make it very clear that the USAF did not merely consider UFOs to be unknown objects or aircraft, but that they are something else altogether, and were not to be confused with known types of objects, including unknown aircraft.
text: Two of the country's best military photo laboratories, the Air Force lab at Wright Field and the Navy's lab at Anacostia, Maryland, had spent many hours trying to prove that the UFO's were balloons, airplanes, or stray light reflections, but they failed - the UFO's were true unknowns.