It doesn't even have to be biological. They could be AI or remotely controlled. You make just as many assumptions while ignoring that MULTIPLE SENSOR SYSTEMS CORROBORATED BY MULTIPLE, CREDIBLE EYEWITNESSES OVER MULTIPLE DAYS, AND IN SOME CASES YEARS are locking on to these things. Things that show intelligent control, and seemingly show up quite often around military assets. Possibly predictably? And, particularly, our nuclear assets.
These events often - but not always - point to physical craft/objects in our skies. You need to come to terms with that. Perhaps advanced black budget tech, or some other country that has made an advancement? Natural phenomena obviously needs to be ruled out, but I think we've passed that point in these cases.