I have an explanation for at least some of these "flying triangle" sightings, based on my own experience.
One clear night, nearly a year ago or so, I was out in the back patio with my then-present-girlfriend doing some observing with the telescope. After observing a good number of clusters, nebula, planets, and double stars, we started chatting about something or other. When suddenly, out of the corner of our eyes we saw something quickly moving in the sky and looked up. Unfortunately we only got a glance at it for a couple of seconds before it moved out of view behind a building. Here are the facts as to what I saw, as I knew them at the time:
o It was a triangular "pattern" of many lights.
o The pattern was quite large, perhaps around 50 to 100 feet (~ 15 - 30 m) across.
o It was low flying, maybe only 100-200 ft (~30-60 m) up.
o It was moving at a modestly fast pace -- not lightning speed, but much faster than something could move using only the wind.
o It was absolutely silent. 'Not a sound to be heard.
..."Did you see that?" My then-girlfriend asked.
..."Yeah... Yeah I did," I replied.
..."What the hell was it?"
..."Um. I don't know."
..."That was weird. What in the world could that have been?" She asked rhetorically.
..."Yeah... That was odd," I muttered.
..."Oh my god," she said slowly, "we just saw a UFO."
..."Hmmm. Perhaps," I said. I started scratching my head. "Maybe it was a group of fighter jets flying in formation and it just seemed closer than it actually was." Which didn't seem too unreasonable as a first guess. Military jets fly overhead all the time in the city I live in.
..."That was no group of planes," she exclaimed. "We would have heard a noise! Even if they were higher it would mean they would had to have been flying faster, and we still would have heard the exhaust."
..."Yes, that makes sense. You're right. One way or another we would have heard a noise. I suppose we can rule out airplanes." I scratched my head, "Maybe a group of gliders?" I felt silly with that statement as soon as it left my tongue. Granted, there is an international glider port in our city, but no gliders would be flying near my neighborhood. And in the middle of the night. And in formation too!
..."Do you even listen to yourself?, she said. "It was a UFO."
..."I suppose you're right."
..."I wonder if anybody else saw this alien ship besides us. Given the direction it was headed..."
..."Hold on," I interrupted. "I'm not saying it was an alien ship. I'm just saying that I don't know what it was."
..."Well what do you think it is, then?"
..."I don't know," I replied. "It was flying. It was some sort of an object or objects. And we haven't Identified it. So technically it's an unidentified flying object until we can identify it. So yeah. At the moment anyway, all we can say is that technically speaking, we saw UFO."
She seemed satisfied with that last comment, so we didn't bring it up again for awhile.
A few days to a week later, I was outside with the telescope again. But this time I was by myself setting it up for an astrophotography attempt. My then-girlfriend was inside watching TV. I had been outside in the dark for awhile, setting up the scope, getting the scope aligned, attaching the focal reducer, fumbling in the dark to find and connect the proper tube attachments, attaching the camera, attaching the cables, connecting the autoguider, the list goes on (astrophotgraphy, as rewarding as it can be, can also be a real tedious b**ch sometimes). My eyes were fairly well adjusted to the darkness, is my point.
Taking a break to smoke a cigarette, I looked up at the sky and low-and-behold the "UFO" came back. And this time I saw it approaching. It was definitely the same thing as before (or something just like it). And this time it flew directly overhead, so I got an even better view. After it passed, I had to sigh and chuckle, realizing what it was. Here are the facts of what I saw:
o It was a triangular "pattern" of many lights. (Just like before.)
o The pattern was quite large. (Same as before.)
o It was low flying. (Same as before.)
o It was moving at a modestly fast pace. (Same as before.)
o It was absolutely silent. (Same as before).
o Each of the 'lights', not only had a main body, but also wings that flapped occasionally.
o Each of the 'lights' also had a neck and head.
o Although most of the lights were not flapping their wings at any given moment in time, each 'light' would flap its wings occasionally.
Yes, this 'UFO' was nothing more than a flock of birds. That's right. A flock of birds.
My back patio that I use for astronomy is fairly well shielded from the surrounding city lights by nearby 2-story buildings. Just on the opposite side of my place, directly across the street, there is a strip mall with atrocious, horrible, pre-regulation, light polluting parking lot lights. My building shields the glare from this strip mall when I'm in the back patio. But anything higher than 2 stories is lit up like a matchbox. The bird flock was flying well over 2 stories up, and were illuminated quite brightly, as can be expected given the light polluting abomination nearby.
So I wonder how many other "flying triangle" sightings could be explained by a flock of birds. If a light source is nearby such that the source is not in direct view; being hid behind a small hill, building, foliage, or some other natural or man-made structure; and if there is little to no fog/haze in the air, one would not even notice that there is such a light source. There would be nothing to reflect the light to one's eyes. But if a flock of birds entered the region of the lights source, they would appear to be lit up quite brightly -- spectacularly if the hidden source was bright enough. Reading through this thread, it doesn't explain all the sightings, at least as they are portrayed. But I bet it could explain quite a few.
After I got my equipment set up and started the first round of exposures, I went back inside where my then-girlfriend was on the couch watching TV.
..."Oh, remember that 'UFO' we saw the other night?" I had to squint my eyes, as they had not yet adjusted to the brightness of the room -- which is saying a lot because the room was only illuminated by a dim table lamp and the TV itself. "I know what it was."
..."Oh, what!" She yelled. "What was it?"
..."I just saw it fly over again a few minutes ago."
..."No!" She exclaimed, "what was it?"
..."It was a flock of birds."
..."No it wasn't."
..."Yes," I said, "it was a flock of birds. I got a good look this time. I even saw their wings flapping. Just birds. 'Wings, head, neck, the whole bit. 'Flock o' birds."
..."It wasn't birds. It was a spaceship or something like that. I don't know if was an alien ship or secret government ship ... I don't know what it was but it was some sort of UFO."
..."No, it's not a UFO anymore," I explained, "I just identified it, so it's no longer an unidentified flying object. It was a flock of birds. I saw it clearly this time."
..."Well, I don't know what it was, but that's not what I saw."
..."We only got a glimpse of it the other night, maybe for only a couple of seconds. But tonight I good view of it. And it went directly overhead this time. I'm tellin' ya', I saw it in detail. 100%, it was a flock of birds."
..."No, my mind's made up. Alien UFO."
I can totally understand somebody seeing something that they can't identify or explain. But why some insist that it must be a spacecraft , is what makes me really think.
and cost the most amount of money.
Looks to much like a spoof to be true, yet not all of them can lie, so it must be an organized spoof, and what other purpuse could it serve, apart from occupying you to worry about them ? 
