There was one on HN last year where Navy pilots saw an object hover above the water then shoot up 10,000 feet in a matter of seconds, hover there, then come back down to the surface. It bounced up and down like that several times then shot off into space. One pilot said the bouncing seemed like a preparation for its eventual takeoff. It was confirmed by Navy radar.

There was a great interview last night on Tucker Carlson where the expert said there are basically two possibilities that the military should explore: one of our terrestrial enemies has an aviation capability more advanced than ours, or an extraterrestrial civilization has capabilities more advanced than us. Of course, there could be some sort of natural phenomenon we don't know about. In any event, it is worth investigating in a rational way.

I don't know about "defying the laws of physics" (since if it could truly defy the laws of the physics that would be whack) but plenty of stealth bombers were reported as "mysterious UFOs" before they were officially revealed in any capacity - and I'm sure there is no shortage of experimental craft that never made the cut.

Hell, even if someone saw a B-2 today they'd probably think it's alien.