As a mere SLF I refrain from posting on PPRUNE lest I offend... Until about 10 years ago I'd have been inclined to subscribe to Carl Jung's explanation for UFOs - ie that they are manifestations of the human psyche - however the sheer accumulation of reports and associated imagery in recent years, plus the release of historical data, have led me to the conclusion that there is no terrestrial explanation.
The release of the images and reports from the Nimitz carrier group events in 2004 would seem to dispel any remaining scepticism. For anyone with only a superficial knowledge of that event I would recommend Commander David Fravor's numerous interviews in which he describes his first hand experience of intercepting the "Tic-Tac" - for example there's an extended session with Joe Rogan on the latter's Spotify site.
There is also an interesting TV series (I forget its title) in which Louis Elizondo and Christopher Mellon (the former being the ex head of the Pentagon's UAP task force and the latter the deputy under secretary of defense for Intelligence) present a mass of highly credible and detailed evidence including the Nimitz events. Obviously as things stand it is impossible to come to any firm conclusion about the source of these events however given that many appear to be so far outside our current technological capacity, not to mention the laws of physics, that it's impossible to assign any "conventional" interpretation.
I'd also recommend a recent documentary "The Phenomenon", which assembles a great deal of fascinating information on this subject. If one is sufficiently critical the sheer volume of highly credible information now in the public domain makes it very hard to dismiss these phenomena as having mundane explanations.