How easy is it to fool people -- even trained people -- over a UFO sighting?
Easy. Just ask Lucy and Lyn Thomas, a UK couple who sparked an international foofooraw by releasing a few dozen floating lanterns -- basically upside-down bags with candles suspended beneath them -- at their wedding in Cardiff. The bags act like balloons, floating away... but these were spotted by police in a helicopter. They were unidentified, sure, but of course this touched off UFO report that got on the 'net, and was reported in New York and India.
I'm of the opinion, given the number of reports like this, that a whole lot of UFO sightings are in fact these floating candle lanterns. I've seen them; they're surprisingly bright. They're small, so from a distance look like a dot, and if it's not too windy they can fly in formation for a long time. They are also, obviously, silent. They don't show up on radar. And if the wind picks up they can suddenly change direction almost as one, moving off at right angles. And, eventually, they can blink out when the candle dies.
Remember: when it comes to UFOs, unknown isn't unknowable, and it usually means you haven't thought the situation through enough yet.