Blips on a radar screen, fuzzy video of lights in the night sky and I witness reports don't cut it.
How our brains reconstruct the visual world and the power of suggestion can make us see what isn't there. We can see what we want to see or what has been suggested by others. Here are some examples... remember the plane that crashed in Queens, New York two months after 9/11? It crashed after it lost its vertical stabilizer from turbulence caused by a plane it was following too close. It crashed in broad daylight and there were hundreds of witnesses. Because it happened right after 9/11 there were many reported seeing it hit my missile, others reported it blew up in mid air and others reported it on fire before it crashed. None of those things were true.
I've had this happen myself. I think it was the 70s when I think it was a news crew caught video of the shinny object flying over a beach I think in California? For years I thought this was the the most compelling UFO video I had ever seen. About 10-15 years ago there was a TV show that rounded up the best UFO video and subjected it it to the best science had to offer. One of the videos they scrutinized was that video, they took it to NASA to have the video enhanced. Turned out to be the sun glaring off a wing of a cessna airplane. The funny thing was when they showed the original footage again I could all of sudden see it was clearly a small plane. None of the dozen of other times I had watched that video did i see a plane.
Another example is the holy grail for UFO sightings, the Roswell "crash". What people forget is just a couple weeks before a guy flying his small plane near Mt. Rainer had reported seeing what he called "flying saucers" in a "V" formation over Mt. Rainer. It was the first time the term flying saucer was used and it was reported in news papers from coast to coast, the country was gripped in flying saucer mania. Police department across the nation were receiving call of people suddenly seeing flying saucers everywhere. I think that's why when Kenneth Arnold found the debris from Project Mogul his mind immediately jumped to flying saucer.