Robin Hanson has a long and very interesting blog post on that question. The point is not to argue that the UFOS are alien beings of some kind, but rather if they were which kinds of theories might help us understand them? Here is just part of Robin’s much longer take:
If the main block to believing in UFOs as aliens is a lack of a plausible enough social theory of aliens, then it seems a shame that almost no one who studies UFOs is a social science theorist. So as such a person, why don’t I step in and try to help? If we can find a more plausible social theory, we could become more willing to believe that UFOs are aliens…
Stylized fact #2: Aliens are rare and self-limited, and yet are here now.
Indirection – We can think of a number of plausible motives for rare limited aliens to make an exception to visit us. First, they may fear us as rivals, and so want to track us and stand ready to defend against us. Second, if their limitation policies are intentional, then they’d anticipate our possibly violating them, and so want to stand ready nearby to enforce their limitation policies on us.
In either of these two cases, aliens might want to show us their power, and even make explicit threats, to deter us from causing problems. And there’s the question of why they don’t just destroy us, instead of waiting around. Third, independent alien origins could be a rare valuable datapoint about far-more-capable aliens who they may fear eventually meeting. In this case they’d probably want to stay hidden longer.
My best bet is this. The vehicles would be “unmanned” drone probes, if only because the stresses of long trips through space would keep the actual alien beings close to home. So the relevant social science question is what kind of highly generalized software instructions you would give such drones. “Seek out major power sources, including nuclear, and seek out rapid flying objects, and then send information back home” would be one such set of instructions roughly compatible with the stylized facts on the ground (or in the air). Of course the information sent back to alien worlds will not be arriving for a very, very long time, so long that the concrete motives of the aliens may not be the major consideration. Collecting the information about other planets across some very long time frame might simply seem worthwhile, relative to the cheap cost of the drone probes. It reminds me a bit of that “put the DNA of all the species on the moon” project we have started, or those seed banks up in the Arctic. Why exactly did we do it? Why not I say!? And yet most humans do not even know those projects are going on.
A further generalized software instruction would be “if approached or confronted, run away fast.” Indeed that is what those flying vehicles seem to do.
The drone probes do not destroy us, because of Star Trek-like reasons: highly destructive species already have blown themselves up, leaving the relatively peaceful ones to send drones around. The drones probably are everywhere, in the galactic sense that is. Yet given the constraints imposed by the speed of light, it is difficult to do much with them that is very useful to the decision-makers that send (sent?) them out. So the relevant theory is one of how advanced civilizations allocate their surplus when there is a lot of discretion and not much in the way of within-lifetime costs and benefits to determine a very particular set of plans and goals. Not even for the grandkids.
In this hypothesis, of course, you have to be short immortality. And short usable wormholes.
By the way, don’t those photos of the drone probes make them look a bit like cheap crap? No tail fins, no “Close Encounters of the Third Kind” music signature, no 3-D holograms, just a superfast vehicle. Like something a second-rate alien non-profit picked up at the local Walmart and sent off into space en masse with solar-powered self-replication. Which is consistent with the view of them being a discretionary resource allocation stemming from projects with fairly fuzzy goals.
A problematic question for any theory is whether competing drone navies have come to visit us, and if so are they fighting over the spoils? Colluding? Hiding from each other? Or what? If aliens are afoot, why should it be only one group of them? That would seem strange, as in most things there are multitudes, at least speaking in Bayesian terms. Aren’t there at least both Klingon probes and Romulan probes, maybe Federation probes too.
Robin’s hypothesis, that they are elatively local panspermiacs, who feel some stake in us, appeals to me. Bayesian logic suggests in any case that the chance of us having resulted from panspermia is pretty high; there are lots of baby civilizations for each parent, so why deny you are probably a baby?
Perhaps our visitors are exercising some “mood affiliation” in wishing to visit and record us! They could be the parents, or perhaps another baby civilization.
Of course since the photos are of such poor quality, and since there is no corroborating evidence of any kind, these UFO sightings probably are not of alien creations, so all of this is pure fantasy anyway.