People forget these kinds of reports go back to the U2 spy plane in the 1950’s. When military members on Guam saw the U2 - while still top secret - take off at a 45 degree angle, the entire island was baffled and didn’t understand what they saw. It’s hard for anyone to wrap their minds around but once upon a time a plane taking off at a 45 degree angle would be as unimaginable as a craft with no heat signature (thoug…
Further back than that, even. AFAIK, the earliest "UFO" reports by military pilots were the so called "foo fighters"[1] which were reported during WWII.