The problem with the idea that they are ‘ours’ is that these things have been seen since long before we had even the technology of our 20th century airplanes.
Jacques Vallee has co-authored a book, ‘Wonders in the Sky’, that is sort of a catalog of historical ‘UFO’ sightings:
https://www.amazon.com/Wonders-Sky-Unexplained-Objects-Antiquity/dp/1585428205
As someone who actually saw swamp gas in action, and who has spent a lot of time gazing at both radar screens and the sky, I’m skeptical.
Time travelers.