During a briefing with reporters, Jon Kosloski, director of the All-domain Anomaly Resolution Office, admitted that the U.S. government is stumped by several “true anomalies.” According to Kosloski, “There are interesting [UFO] cases that I, with my physics and engineering background and time in the [intelligence community], I do not understand. And I don’t know anybody else who understands them either.”
That’s assuming they actually move as described, and it’s not an illusion because the observer is also moving, or is trying to gauge speed or direction of an object against the sky, with no visual references. The human eye is pretty bad at that.