Years ago, my neighbor shot an intruder in his house. It was very early in the morning. I heard the shot, but thought it must have been a power transformer blowing up, or some idiot setting off a cherry bomb.
Not until the cops and ambulance showed up, and the cops pounded on my door to ask what I had heard, did I realize what happened.
So, you hear the sound of a plane crashing, but you think it's a distant gunshot from a hunter, or heat lightning, or whatever. Your mind doesn't recognize it as something worse, like a plane crash, unless you see it going down. Easy for such a thing to get lost.
This past summer, went to dinner at a riverfront restaurant at the Jersey Shore. While we were eating dinner, an experimental airplane took a nosedive into a nearby marina, a short walk away. We didn't notice a thing, nor did anyone else in the restaurant. We did see a couple of State Police boats motor up the river, but guessed it was their end of patrol or something.
We read about the crash in the newspaper the next day.
Yes, if his engine cut out and he glided into a crash there would have been little noise.