Davis-Monthan Air Force Base outside Tucson, Arizona is home to the United States Air Force 355th Fighter Wing, making it an 'active' air force base. However, what it is best known for is its hosting of the AMARG, or Aerospace Maintenance and Regeneration Group. This unit receives for storage all out of use aircraft and 'aerospace vehicles' from the U.S. military and NASA (as well as various allies occasionally) and stores them in various states of preservation. Some aircraft are in safe storage and can be re-activated in order to be rebuilt to a newer variant, or to replace operating losses. Some are used for parts. Some may be sold or transferred later to allied nations or customers. The upshot of it all, though, is that in the Arizona desert there are over 4,200 aircraft sitting quietly waiting to see what will happen to them. This makes for incredibly impressive vistas, and the airplane graveyard there has been featured in all manner of movies, music videos and documentaries. The Discovery Channel and the Military Channel seem to find reasons to go there at least once a year.
In addition to AMARG, Davis-Monthan is used for the training and basing of A-10 and OA-10 units - the surrounding desert, excellent for ranges, makes for perfect low-level training terrain. There is a unit of EC-135 Compass Call electronic warfare aircraft based there, although their unit is headquartered with the 55th Wing at Offutt AFB in Nebraska.