Highly trained pilots are still subject to the same cognitive biases that most folks are. The important thing is whether or not the claims are evaluated rigorously and scientifically. And every single time that the due diligence is put into these claims the result is that the "UFO" is identified as very likely something else such as a balloon or another plane.

This alone is a problem because it completely inverts the burden of proof. The burden should be that the very first step is to put in the rigorous work to identify anything it might be that is a mundane explanation, and only then to put together a strong case of positive evidence that there is something odd and unexplainable going on. However, that's not the way these things have been going. Instead the typically pattern is a half-assed investigation at the level of "I dunno, it looks weird" followed by jumping to the conclusion that something that "looks weird" must be an alien spaceship or a classified spy plane or something. And so instead it falls to a small group of amateurs to actually put in the work and then they'll come back and say "oh yeah, this is actually a video of another plane, and here's the exact plane it was", which is an unreasonable level of burden for them, but that's the sorry state things are in because so many people are so biased toward wanting to believe these things are alien spacecraft.