The stealth bomber was a UFO for quite some time. A number of commercial pilots saw oddly-shaped craft from their 30,000 ft vantage point, craft that were faster than any known human plane, went up and down in ways that human planes didn’t… and the airline would send the pilot for a psych exam if he insisted on reporting it. Because ABQ ATC (and a number of others) were absolutely vehement that their radar showed no such thing.