Area 51 providers (including Russian providers and the IKONOS) are commercially available. These show the runway markings, base facilities, aircraft, and vehicles. When documents that mention the Nevada Test Site (NTS) and operations at Groom are declassified, mentions of Area 51 and Groom Lake are routinely redacted. One exception is a 1967 memo from CIA director Richard Helms regarding the deployment of three OXCART aircraft from Groom to Kadena Air Base to perform reconnaissance over North Vietnam. Although most mentions of OXCART's home base are redacted in this document, as is a map showing the aircraft's route from there to Okinawa, the
Area 51 show what appears to be F-16 Fighting Falcon aircraft stationed on the base. Its secretive nature and undoubted connection to classified aircraft research, together with reports of unusual phenomena, have led Area 51 to become a focus of modern UFO and other conspiracy theories. Some of the activities mentioned in such theories at Area 51 include: Many of the hypotheses concern underground facilities at Groom or at Papoose Lake (also known as "S-4 location"), south, and include claims of a transcontinental underground railroad system, a disappearing airstrip (nicknamed the "Cheshire Airstrip", after Lewis Carroll's Cheshire cat) which briefly appears when