It's good to play as the bad guy

The squadron emblem

Many people wanted to know what those lights were in the Nevada skies in the 70s through the 90s. People theorized that it was flying saucers, experimental spacecraft, or UFOs of alien origin, but now we have a good idea of what most of them may have been after Constant Peg (and the F-117) was declassified. 

A picture of the US crews in front of a MiG-21 from the 4477th. Sourced from Wikipedia.

What is Constant Peg, you ask? Well, it was the name of the longest continuing classified military airplane program done by the United States. Nestled in a remote locale in Nevada, is the Tonopah Test Range, with it's accompanying airfield which was home to the 4477th Test and Evaluation Squadron, which was a joint-service effort with pilots/aviators from the Navy, USMC, and Air Force, that was also sometimes supported by the infamous Groom Lake facility. This unit was given the classified assignment described as "the testing and evaluation of foreign aircraft technology" from the years of 1977 to 1990.  

A Constant Peg MiG-23 flying over the Nevada desert.

Basically, the military had been able to acquire a relatively large amount of MiG-21s, MiG-23s, MiG-27s, Chinese copies of these planes, and others through various means, such as: political dealings, espionage, straw purchases, defections, captured, recovered from crashes, and even stolen examples. Ultimately, the Air Force (and other services) were eager to form a squadron to evaluate them and put them to use against American aircraft and pilots in wargames. Both to assess their performance and capabilities of the expected adversary aircraft, as well as understand the workings of the aircraft to better prepare US pilots against them in the event of a future war, and current proxy conflicts.

Another MiG-23 of the squadron. 

The pilots selected for this mission were to be the absolute best of their fields, and would train relentlessly, as they not only had to fly missions as test pilots to evaluate the performance limits of the planes themselves, but also to fly as adversary aggressor pilots to other American aircrews. The pilots were extremely professional and dedicated to the mission, even to the point of speaking Russian when on comms with other American aircrews. 

Constant Peg MiG-17 at the front, Mig-21 at the rear

As amazing as all this sounds, the real miracle of the whole story is the ground crews and maintainers of the aircraft, who were often very senior NCOs, a large number of which had served in the Thunderbirds. This was required as they needed to basically reverse engineer how to support these Russian planes with everything still labelled in Russian, with no manuals, translations, or original support crews to speak of to assist. Nothing short of astounding when you thing about that feat!

At the end of the day, I can't really do it enough justice with just a small blog write up with a few pictures. So here's a short 5 min documentary on youtube on the subject. Also, I embedded below, and even more excellent video from the 10% True youtube channel that has a couple of Constant Peg veterans commenting on recently declassified footage at Tonopah of the 4477th operations:

I think the final and most definitive work on the subject will have to be the book available by Col. Gail Peck (retired) who headed the project, which is available on Amazon:

Though, don't be fooled by the fact the squadron officially stood down in 1990, as our story doesn't end there. It was known that after the 4477th stood down, the remaining assets were reconstituted as Detachment 3 of 53rd Test and Evaluation Group, who flew much more modern threat aircraft such as MiG-29 Fulcrums and Su-27 Flankers. This was also disbanded, but is now likely operating those assets as a part of the 422d Test and Evaluation Squadron, with their aircraft likely being based out of Groom Lake itself now. It seems even locals have documented them showing up from time to time. So if you can hear or see military fighter jets in the skies of Nevada, you may want to take a closer look, to see if they are Russian in origin.