Something I've seen several times is bright objects that travel at speed and then suddenly make drastic changes in trajectory, in a way that would be impossible for any man-made craft like planes or helicopters. Definitely not satellites which move fast, but in a predictable orbit. No idea what they are.
I think there is a case in Blue Book where a group of astronomers was outside in a backyard for a party and they all observed a star that moved erratically and then it followed an arc perfectly along the edge of the moon. The creepy thing is that the analysts calculated that the arc only lined up with the edge of the moon within a small distance of the backyard where the astronomers were located. (That claim seems a bit fishy to me, but I don't know the specifics.) Anyway, it was as if the light was performing specifically for the group of astronomers that were observing it. That seems to be fairly common with UFOs. The human observes the UFO, but the UFO is very aware of the human observer and often reacts. Sometimes beams of light shine to the ground. Sometimes the UFO zooms closer.
I observed a disc in the afternoon several years ago, and it seemed to be aware of me. I observed it for several minutes and even left briefly to find my camera and returned without losing sight of it. Then as soon as I bent over to pick up the camera, the disc was gone. It might have been coincidence, but I had a creepy feeling that the UFO had been watching me all the time. It made me angry, because I only planned to get a closer look through the zoom lens. My camera was not capable of taking a good picture of something so small, but my eyes could have seen it better with magnification. I really wanted to see it in more detail to know what it was for certain. I have wondered if it was a helicopter reflecting light that suddenly changed orientation so that it no longer reflected light. IDK
EDIT: Another odd thing about my sighting was that I had been obsessed with UFOs and rereading all the classic cases for a week before it happened. I was really depressed and wanted to know the answer on UFOs, and then as if on cue a UFO appears. A single observer who is obsessed with seeing a UFO (i.e. me
) is not reliable evidence unfortunately.