Heat ripples rise off the desert floor as seen through a barb-wired fence as a pickup drives past stored military aircraft at the 309th Aerospace Maintenance and Regeneration Group boneyard, Thursday, May 21, 2015, in Tucson, Ariz. The 309th is the United States Air Forces aircraft and missile storage and maintenance facility and provides long and short-term aircraft storage, parts reclamation and disposal. (AP Photo/Matt York) A field of Lockheed C-5 Galaxy cargo jets are seen through a window from another C-5 at the 309th Aerospace Maintenance and Regeneration Group boneyard at Davis-Monthan Air Force Base in Tucson, Ariz., on Thursday, May 21, 2015. The C-5A Galaxy is the largest aircraft in the U.S. armed services. The C-5 has a wingspan of over 222 feet and stands over 65 feet high has been used by the Air Force continually since 1969. (AP Photo/Matt York)U.S. Marines work atop an F/A-18 at the 309th Aerospace Maintenance and Regeneration Group boneyard in Tucson, Ariz. on Thursday, May 21, 2015. The Marines are repairing F/A-18's to return to service at the 309th facility. (AP Photo/Matt York) A demilitarization crew member removes components from the cockpit of an F-4 Phantom slated for destruction at the 309th Aerospace Maintenance and Regeneration Group boneyard in Tucson, Ariz., on Thursday, May 21, 2015. The 309th is the United States Air Forces aircraft and missile storage and maintenance facility and provides long and short-term aircraft storage, parts reclamation and disposal. (AP Photo/Matt York) Phil Kovaric and Dennis Varney remove the missile rails from an F-4 Phantom slated for destruction at the 309th Aerospace Maintenance and Regeneration Group boneyard in Tucson, Ariz. on Thursday, May 21, 2015. The 309th is the United States Air Forces aircraft and missile storage and maintenance facility and provides long and short-term aircraft storage, parts reclamation and disposal. (AP Photo/Matt York) F-16 Fighting Falcons sit in a field along Miami St. at the 309th Aerospace Maintenance and Regeneration Group boneyard, Thursday, May 21, 2015, at Davis-Monthan Air Force Base in Tucson, Ariz. Over 4,500 variants of the F-16's have been produced since 1973. This field of fighters will become drone target planes in the future. (AP Photo/Matt York)F-16 Fighting Falcons covered in sealing paint sit in a field along Miami St. at the 309th Aerospace Maintenance and Regeneration Group boneyard at Davis-Monthan Air Force Base in Tucson, Ariz., on Thursday, May 21, 2015. Over 4,500 variants of the F-16's have been produced since 1973. This field of fighters will become drone target planes in the future. (AP Photo/Matt York)A Boeing Vertol CH-46 Sea Knight, tail no. 153993, is stored at the 309th Aerospace Maintenance and Regeneration Group boneyard at Davis-Monthan Air Force Base in Tucson, Ariz. on Thursday, May 21, 2015. According to the U.S. Marine Corps, this helicopter was the last aircraft out of Vietnam. Known by its mission name, Swift 2-2, this CH-46 lifted the remaining 11 members of the Marine Guard off the roof of the U.S. Embassy in Saigon just before 8:00 a.m. on April 30, 1975. It was the last aircraft to touch and leave the U.S. embassy as North Vietnamese tanks breached defenses on the outskirts of Saigon as the Vietnam War came to an end. (AP Photo/Matt York)The 39th and final B-52G Stratofortress, tail number 58-0224, right, accountable under the New START Treaty (Strategic Arms Reduction Treaty) with Russia, lies in the 309th Aerospace Maintenance and Regeneration Group boneyard at Davis-Monthan Air Force Base in Tucson, Ariz. on Thursday, May 21, 2015. The United States cut the tails off the 39 aircraft in order to remove the B-52G models from treaty accountability, as they still count as nuclear-capable delivery platforms with their tails attached. The tails are angled at 30 degrees so Russian satellites can view compliance. Tail number 58-0224, nicknamed "Sweet Tracy," flew combat missions over North Vietnam in Operation Linebacker II, which began Dec. 18, 1972 and lasted 11 nights. The aircraft targeted the Yen Vien Railroad Yards and the Hanoi Railroad Repair Yards. (AP Photo/Matt York)In this photo taken on Friday, May 15, 2015, crew from from the 309th Aerospace Maintenance and Regeneration Group boneyard prepare a pair of Boeing Vertol CH-46 Sea Knight helicopters for storage after their arrival at Davis-Monthan Air Force Base in Tucson, Ariz. The 309th is the United States Air Force's aircraft and missile storage and maintenance facility. AMARG provides long and short-term aircraft storage, parts reclamation and disposal. (AP Photo/Matt York)Crew members from the 309th Aerospace Maintenance and Regeneration Group boneyard secure a U.S. Navy Lockheed P-3C Orion anti-submarine aircraft at its storage site after its arrival at Davis-Monthan Air Force Base in Tucson, Ariz. on Friday, May 15, 2015. (AP Photo/Matt York)In this photo taken on Friday, May 15, 2015, crew from the 309th Aerospace Maintenance and Regeneration Group boneyard prepare to remove engine fluid from a Bell OH-58 Kiowa helicopter after its arrival at Davis-Monthan Air Force Base in Tucson, Ariz. The OH-58 has been in continuous use by the U.S. Army since 1969 and seen combat in every conflict since Vietnam. (AP Photo/Matt York)Various military aircraft, including F-15's, C-130's and F-4's are arranged behind the wing of a Lockheed C-5 Galaxy Cargo Jet at the 309th Aerospace Maintenance and Regeneration Group boneyard at Davis-Monthan Air Force Base in Tucson, Ariz. on Friday, May 15, 2015. With a wingspan over 222 feet, the C-5A Galaxy the largest aircraft in the U.S. armed services. (AP Photo/Matt York)In this photo taken on Thursday, May 14, 2015, the sun sets over C-130 cargo planes at the 309th Aerospace Maintenance and Regeneration Group boneyard at Davis-Monthan Air Force Base in Tucson, Ariz. The 309th is the United States Air Force's aircraft and missile storage and maintenance facility and provides long and short-term aircraft storage, parts reclamation and disposal. (AP Photo/Matt York)In this photo taken on Thursday, May 14, 2015, C-130 Hercules cargo planes are lined up in a field at the 309th Aerospace Maintenance and Regeneration Group boneyard at Davis-Monthan Air Force Base in Tucson, Ariz. Over 2,300 variants of the C-130 have been produced since 1954. (AP Photo/Matt York)309th Aerospace Maintenance and Regeneration Group employees walk past Boeing KC-135R Stratotankers at the boneyard, Thursday, May 14, 2015 at Davis-Monthan Air Force Base in Tucson, Ariz. The "boneyard" is worlds largest aircraft storage and preservation facility. (AP Photo/Matt York)In this photo taken on May 14, 2015, an Army Sikorsky VH-34s Choctaw helicopter, which was used to transport President Dwight D. Eisenhower, sits in a field at the 309th Aerospace Maintenance and Regeneration Group boneyard at Davis-Monthan Air Force Base in Tucson, Ariz. Eisenhower became the first chief executive to be transported by helicopter and the VH-34's served as "Army One" from 1958 through 1963 for Eisenhower and President John F. Kennedy. (AP Photo/Matt York) In this photo taken on Thursday, May 14, 2015, the remains of a Boeing KC-135A Stratotanker, serial no. 55-3129, are stored at the 309th Aerospace Maintenance and Regeneration Group boneyard at Davis-Monthan Air Force Base in Tucson, Ariz. The aircraft is the original "Weightless Wonder" of NASA according to the planes' records. NASA used the aircraft to train the Mercury 7 astronauts on zero-gravity flights, and it was nicknamed the "Vomit Comet" for its effect on pilots and passengers alike. (AP Photo/Matt York)One of the few civilian aircraft on site, a Boeing 707, serial no.TWA N28714, sits in the aircraft battle damage repair area at the 309th Aerospace Maintenance and Regeneration Group boneyard, Thursday, May 14, 2015 at Davis-Monthan Air Force Base in Tucson, Ariz. On August 29, 1969, members of the Popular Front for the Liberation of Palestine (PFLP), including former Palestinian National Council member Leila Khaled, hijacked the aircraft, call sign TWA 840, believing that then-Israeli ambassador to the United States Yitzhak Rabin was aboard. When discovered he was not on the aircraft, the hijackers flew to Syria and released all but 2 Israeli passengers. The hijackers proceeded to explode a bomb in the cockpit after the hostages had disembarked. Extensive repairs put the aircraft back into serve until 1980. (AP Photo/Matt York)A row of McDonnell Douglas F-4 Phantom II's are stored at the 309th Aerospace Maintenance and Regeneration Group boneyard, Thursday, May 14, 2015 at Davis-Monthan Air Force Base in Tucson, Ariz. (AP Photo/Matt York)