I’ve seen a couple. First and most memorable was early 70s. Mtn Home had just acquired the F-111s. We knew of the horrible history of crashes. It was fairly early in the morning and I had just exited the hallway to look out the front windows that faced Bennett Mtn. I saw a bright silver orb, the color of magnesium burning crest the foothills from the East. It proceeded in a westerly direction following the terrain. It was between us and the top of Bennet Mtn. so around 5 to 7k feet. It was not traveling supersonic and it emitted no sound nor a smoke or exhaust plume. Based on the distance from where I stood and where relation to the size of the Mtn for me it looked to be the size of a watermelon.
Mom was on the phone with dad at the AFB and said OMG a plane is crashing. Dad mentioned it to several folks at the AFB and learned that it was being tracked. Later it was disclosed as a “fireball”. Yeah. I don’t think so, not traveling subsonic and following the terrain!