When virtually everyone carries a high resolution camera in their pocket, if this was anything but a military-focused phenomenon we would have plenty of video. Why no UFO sightings by private pilots, sports enthusiasts in remote places, from ordinary citizens through the windows of commercial aircraft - just to name a few scenarios that ought to occur with similar frequency if these were random events.
Speaking of witnesses ...
https://en.wikipedia.org/wiki/2006_O%27Hare_International_Airport_UFO_sighting