When humans first flew with lighter than air craft, there were sightings of UFO flying balloons.
Then, as airplanes became more prevalent, sightings of aircraft like UFOs became prominent.
Now, drones. There was a locally well publicised event that took place a few years ago over northeastern Colorado, southeastern Wyoming and Western Nebraska- where there are lots of both decommissioned and still active nuclear missile silos. Dozens of drones were observed by local residents, police, sheriff's department and other government officials and even military personnel over the course of MONTHS flying around, night after night, apparently surveying the area.
I don't think they were extraterrestrial because they had lights and were operating as one would expect drones to operate but local military sources denied they had anything to do with them. I don't believe that for a minute, although it's perfectly plausible that one military organisation (maybe surveillance or testing) may not be telling the others (say, missile defense command) what they're doing.