Question: What defense contractor operated a highly classified fleet of passenger aircraft to transport United States Air Force military and contractor employees?

Context articles: Beechcraft T-6 Texan II
Georgia Nuclear Aircraft Laboratory
Keyway Air Transport
Black project
Air Base Ground Defense
Military Air Transport Service
Hanoi Taxi
Uniforms of the United States Air Force
Tin City LRRS Airport
Janet (airline)

The Beechcraft T-6 Texan II is a single-engine turboprop aircraft built by the Raytheon Aircraft Company (which became Hawker Beechcraft and later Beechcraft Defense Company, and was bought by Textron Aviation in 2014).
 A trainer aircraft based on the Pilatus PC-9, the T-6 has replaced the Air Force's Cessna T-37B Tweet and the Navy's T-34C Turbo Mentor.
 The T-6A is used by the United States Air Force for basic pilot training and Combat Systems Officer (CSO) training and by the United States Navy and United States Marine Corps for primary Naval Aviator training as well as primary and intermediate Naval Flight Officer (NFO) training.
 The T-6A is also used as a basic trainer by the Royal Canadian Air Force (CT-156 Harvard II), the Greek Air Force, the Israeli Air Force ("Efroni"), and the Iraqi Air Force.
 The T-6B is the primary trainer for U.S. student naval aviators.
 The T-6C is used for training by the Mexican Air Force, Royal Air Force, Royal Moroccan Air Force, and the Royal New Zealand Air Force.
The Georgia Nuclear Aircraft Laboratory, also known as AFP No. 67, for Air Force Plant 67 was a United States Air Force test facility located in the Dawson Forest in Dawsonville, Georgia.
 It was the site of Lockheed's lab for investigating the feasibility of nuclear aircraft.
 The site was used for irradiating military equipment, as well as the forest to determine the effect of nuclear war, and its effects on wildlife.
 The area was closed in 1971 and acquired by the city of Atlanta for a second airport, but its topography was determined to be ill-suited for an airport.
 Documents explaining what went on at the site remain highly classified, and the entrance to the underground portion of the facility has been buried.
 The only objects left above ground were the concrete foundations on which the buildings and reactors were placed.
Keyway Air Transport was a United States airline that operated from Frankfurt International Airport (which at the time was also home to a United States Air Force facility; Rhein-Main Air Base) using a Boeing T-43 Bobcat (a military variant of the Boeing 737-200) and a Boeing 707-355C.
 Details on its operation are unknown.
 The 737-200 was operated by Keyway Air Transport from 1986 up until 1992, when it was transferred to defence contractor EG&G, who operated the aircraft in the Janet fleet up until 2009 when it was retired from service.
 The Boeing 707-355C was operated from 1986 up until 1989, when it was transferred to HCL Aviation.
 From 1992 onwards, after having been modified for military service by Raytheon, the aircraft was used by the United States Air Force as an airborne command post for the United States Central Command and later on was reported as being used by the Air Force Special Operations Command, before being put in storage at the 309th Aerospace Maintenance and Regeneration Group located on Davis–Monthan Air Force Base in 2002.
A black project is in the vernacular of the United States and United Kingdom militaries, a highly classified military or defense project, unacknowledged publicly by the government, military personnel, or defense contractors.
 Examples of U.S. military aircraft developed as black projects include the F-117 Nighthawk stealth attack aircraft and the B-2 Spirit stealth bomber, both of which were highly classified and denied as existing until ready to be announced to the public.
 In the United States the formal term is "Special access program (SAP)".
Air Base Ground Defense (ABGD) is the operational term used by the United States Air Force to denote ground combat operations in defense of U.S. Air Force bases.
 This specialty is filled by members of the Air Force Security Forces, who serve not only as Police/Law Enforcement officers, but also as ground combat troops in defense of U.S. air bases around the world.
 In this capacity, their duties are similar to those performed by the RAF Regiment and Royal Air Force Police of the British Royal Air Force, namely, to conduct ground combat operations as highly trained infantry troops, law enforcement and security in defense of U.S. air bases.
 Camp Bullis in Texas is where all levels of Air Base Ground Defense (ABGD) are instructed, the course ranges in length from 4–6 weeks.
 In these weeks of training Air Force Security Forces are taught to operate the following weapons: M-4 Carbine, M-9, M-203, M-240B, M-249 (SAW), MK-19, M67 (hand grenade), M18A1 (Claymore mine), and the M-72 (LAW rocket),M-60 as well as other base defense weapons and tools.
The Military Air Transport Service (MATS) is an inactive Department of Defense Unified Command.
 Activated on 1 June 1948, MATS was a consolidation of the United States Navy's Naval Air Transport Service (NATS) and the United States Air Force's Air Transport Command (ATC) into a single joint command.
 It was inactivated and discontinued on 8 January 1966 when the Air Force and Military Airlift Command (MAC) as a separate strategic airlift command and returned shore-based Navy cargo aircraft to Navy control as operational support airlift (OSA) aircraft.
Hanoi Taxi is a Lockheed C-141 Starlifter strategic airlift aircraft (serial number 66-0177) that was in service with the United States Air Force and became famous for bringing back the first returned prisoners of war in Operation Homecoming.
 This aircraft, which was delivered to the Air Force in 1967, was the last C-141 to be withdrawn from service after a career of almost 40 years, as the last of the fleet was retired in 2006 as sufficient C-17 Globemaster III aircraft became available in the regular Air Force to allow C-141s still serving with Air Force Reserve units to be replaced by the C-5 Galaxy aircraft being seconded from the regular Air Force.
 The "Hanoi Taxi" is currently housed at the National Museum of the United States Air Force, near Dayton, Ohio.
The United States Air Force uniform is the standardized military attire worn by airmen of the United States Air Force.
 Specific Air Force Instructions address standardized wear that is identical for members of both the Active Component (i.e., the Regular Air Force) and that of the service's two reserve components that comprise the Air Reserve Component, that being the Air Force Reserve and the Air National Guard.
 This includes personnel in the Air Force's sole enlisted accession program, Basic Military Training (BMT), and the three USAF commissioned officer accession programs: Officer Training School (OTS) officer trainees, college/university level Air Force Reserve Officers' Training Corps (AFROTC) cadets and United States Air Force Academy (USAFA) cadets.
 Provisions are also included for authorized wear on certain occasions by honorably retired career members of the Air Force, to also include retirees of both the Air Force Reserve and the Air National Guard.
Tin City Airport is a United States Air Force military airstrip.
 Its mission is to provide contractor access to the Tin City Long Range Radar Station for equipment servicing and other requirements.
A highly classified small fleet of passenger aircraft known as "Janet" is operated for the United States Air Force to transport military and contractor employees.
 It mainly serves the Nevada National Security Site (most notably Area 51 and TTR), from their terminal at Las Vegas' McCarran International Airport.
 The fleet's "Janet" call sign, from which its "de facto" name comes, is said to stand for "Just Another Non-Existent Terminal".