Myself and my roommate were driving south down 25 from Fort Collins to Denver to see a concert. It was dark, and as usual, there were a lot of helicopters in the sky on the drive. I always watch these with mild interest hoping to see a light that does something it 'shouldn't' so to speak. Until today I'd never seen something that was very clearly not a normal human aircraft. We were heading about through Longmont and I was looking out the passenger window when we went behind a bit of a ridge, obstructing the mountains and the development to the west of the expressway. When they came back into view, there were three large white/gold/silver fireball like lights in the sky over the mountains. I stared at them for a few seconds before I pointed them out to my roommate, who agreed immediately with me that they were not normal. In fact, a couple of weeks ago, him and one or two of my other roommates saw something very similar, although from a much farther distance, so the lights themselves were less spectacular, and the trails they left behind weren't visible. The three fireballs were initially arranged in an equilateral triangular pattern pointing down towards the mountains. Very clearly near the middle were two bright white helicopter lights, where they were in regards to distance in relation to myself and the other lights though I'm not too sure. The three lights then started to almost swirl around, and fly sporadically in different directions, including up and down. When they changed direction, their tail sort of seemed to lead out in front of them like it was propelling them. the tails were about as long as the spherical center of the lights, which was maybe the size of half a dime held at arms length. They kept moving like this for a minute or so, and two of them disappeared briefly and reappeared in that time. After a minute and a half or two minutes total time, they started to lose altitude and one seemed to fall behind the mountain range. The other two, however, fell in front of it, as I could see car headlights behind them. Both of them seemed to pick up a decent bit of velocity southward before we drove behind a ridge, lost sight, and didn't see them upon getting a clear view again. After seeing these, me and my roommate were in an awe that lasted most of the night. He has seen a dark triangle before, but I'd never witnessed something like this with my own eyes, it was pretty cool.