The Lockheed U-2, nicknamed "Dragon Lady", is a single-engine, very high-altitude surveillance aircraft flown by the United States Air Force and previously flown by the Central Intelligence Agency. It provides day and night, very high-altitude (70,000 feet/21,000 meters), all-weather surveillance. The aircraft is also used for electronic sensor research and development, satellite calibration, and satellite data validation.
In the early 1950s, with Cold War tensions on the rise, the U.S. military required better strategic reconnaissance to help determine Soviet capabilities and intentions. The existing surveillance aircraft were primarily converted bombers, vulnerable to anti-aircraft artillery, missiles, and fighters. It was thought an aircraft that could fly at 70,000 feet (21,000 m) would be beyond the reach of Soviet fighters, missiles, and even radar. This would allow "overflights"knowingly violating a country's airspace to take aerial photographs.
The Air Force gave contracts under the code name "AQUATONE" to Bell Aircraft, Martin Aircraft, and Fairchild Engine and Airplane to develop proposals for the new reconnaissance aircraft. Officials at Lockheed Aircraft Corporation heard about the project and asked aeronautical engineer Clarence "Kelly" Johnson to come up with a design. Johnson was a brilliant designer, responsible for the P-38 Lightning, and the P-80. He was also known for completing projects ahead of schedule, working in a separate division of the company jokingly called the Skunk Works.
Johnson's design, called the CL-282, married long glider-like wings to the fuselage of another of his designs, the F-104 Starfighter. To save weight, his initial design didn't even have conventional landing gear, taking off from a dolly and landing on skids. The design was rejected by the Air Force, but caught the attention of several civilians on the review panel, notably Edwin Land, the father of instant photography. Land proposed to CIA director Allen Dulles that his agency should fund and operate this aircraft. After a meeting with President Eisenhower, Lockheed received a $22.5 million contract for the first 20 aircraft. It was renamed the U-2, with the "U" referring to the deliberately vague designation "utility".
The first flight occurred at the Groom Lake test site (Area 51) on 1 August 1955, during what was only intended to be a high-speed taxi run. The sailplane-like wings were so efficient that the aircraft jumped into the air at 70 knots (130 km/h).
James Baker developed the optics for a large-format camera to be used in the U-2 while working for Perkin-Elmer. These new cameras had a resolution of 2.5 feet (76 cm) from an altitude of 60,000 feet (18,000 m). Balancing is so critical on the U-2 that the camera had to use a split film, with reels on one side feeding forward while those on the other side feed backward, thus maintaining a balanced weight distribution through the whole flight.
When the first overflights of the Soviet Union were tracked by radar, the CIA initiated Project RAINBOW to reduce the U-2's radar cross section. This effort ultimately proved unsuccessful, and work began on a follow-on aircraft, which resulted in the Lockheed A-12 Blackbird.
Pratt & Whitney J75 turbojet engine from a U-2 shot-down (Cuba 1962) on display in museum in Havana
The unique design that gives the U-2 its remarkable performance also makes it a difficult aircraft to fly. It was designed and manufactured for minimum airframe weight, which results in an aircraft with little margin for error. Most aircraft were single-seat versions, with only five two-seat trainer versions known to exist. Early U-2 variants were powered by Pratt & Whitney J57 turbojet engine. The U-2C and TR-1A variants used a more powerful Pratt & Whitney J75 turbojet. The U-2S and TU-2S variants incorporated an even more powerful General Electric F118 turbofan engine.
High-aspect-ratio wings give the U-2 some glider-like characteristics, with a lift-to-drag ratio estimated in the high 20s. To maintain their operational ceiling of 70,000 feet (21,000 m), the U-2A and U-2C models (no longer in service) must fly very near their maximum speed. However, the aircraft's stall speed at that altitude is only 10 knots (19 km/h) less than its maximum speed. This narrow window was referred to by the pilots as the "coffin corner". For 90% of the time on a typical mission the U-2 was flying within only five knots above stall, which might cause a decrease in altitude likely to lead to detection, and additionally might overstress the lightly built airframe.
U-2 at The Imperial War Museum, Duxford
The large wingspan and resulting glider-like characteristics of the U-2 make it highly sensitive to crosswinds which, together with its tendency to float over the runway, makes the U-2 notoriously difficult to land. This results in a required chase car (usually a "souped-up" performance model including a Ford Mustang SSP, a Chevrolet Camaro B4C, and most recently a Pontiac GTO) and assistant who "talks" the pilot down by calling off the declining height of the aircraft in feet as it decreases air speed in order to overcome the cushion of air provided by the high-lift wings in ground effect. Instead of the typical tricycle landing gear, consisting of a nose wheel and two sets of main wheels, one under each wing, the U-2 uses a bicycle configuration, with the forward set of main wheels located just behind the cockpit and the rear set of main wheels located behind the engine, coupled to the rudder in order to provide taxi steering.
To maintain balance while taxiing for takeoff, the ground crew installs two auxiliary wheels, called "pogos". These fit in sockets under each wing at about mid-span, and fall onto the runway as the aircraft takes off. To protect the wings during landing, each wingtip has a titanium skid. After the plane comes to a halt, the ground crew re-installs the pogos. The first pogo goes on the "light" or "up wing" while the other crew members use their weight to pull down the light side. Then two of the crew push up the heavy wing, allowing a third crew member to install a pogo on the other side.
Because of the high operating altitude the pilot must wear the equivalent of a space suit. The suit delivers the pilot's oxygen supply and emergency protection in case cabin pressure is lost at altitude (the cabin provides pressure equivalent to about 29,000 feet/8,800 metres). To prevent hypoxia and decrease the chance of decompression sickness pilots don a full pressure suit and begin breathing 100% oxygen one hour prior to launch to de-nitrogenize the blood; while moving from the building to the aircraft they breathe from a portable oxygen supply.
The aircraft carries a variety of sensors in the nose, Q-bay (behind the cockpit, also known as the camera bay), or wing pods. The U-2 is capable of simultaneously collecting signals, imagery intelligence and air samples. Imagery intelligence sensors include either wet film photo, electro-optic or radar imagery the latter from the Raytheon ASARS-2 system. It can use both line-of-sight and beyond-line-of-sight data links. One of the most unusual instruments in the newest version of the U-2 is the off-the-shelf Sony video camera that functions as a digital replacement for the purely optical viewsight (an upside down periscope-like viewing device) that was used in older variants to get a precise view of the terrain directly below the aircraft, especially during landing.
 Operational history
 United States
U-2 testing aboard USS America (CV-66).
One of NASA's ER-2s in flight over the California desert. A NASA ER-2 set the world altitude record for its weight class
Though the U.S. Air Force and Navy would eventually fly the U-2, it was originally a CIA operation, run through the Office of Scientific Intelligence. Due to the political implications of a military aircraft invading a country's airspace, only CIA U-2s conducted overflights. The pilots had to resign their military commissions before joining the CIA as civilians, a process they referred to as "sheep dipping".
As often happens with new aircraft designs, there were several operational accidents, some fatal. The first fatal accident was on 15 May 1956, when the pilot stalled the aircraft during a post-takeoff maneuver which was intended to drop off the wingtip outrigger wheels. The second occurred three months later, on 31 August when the pilot stalled the aircraft immediately after takeoff. Two weeks later, a third aircraft disintegrated during ascent, also killing the pilot. There were a number of other non-fatal incidents, including at least one which resulted in the loss of the aircraft.
The U-2 came to public attention when CIA pilot Francis Gary Powers was shot down over Soviet territory on 1 May 1960, causing the U-2 incident.
On 14 October 1962, a U-2 from the 4080th Strategic Reconnaissance Wing, based at Laughlin Air Force Base near Del Rio, Texas, and piloted by Major Richard S. Heyser, photographed the Soviet military installing nuclear warhead missiles in Cuba, precipitating the Cuban Missile Crisis. Heyser concluded this flight at McCoy AFB in Orlando, Florida, where the 4080th established a U-2 operating location for the duration of the crisis. On 27 October 1962, in flight from McCoy AFB, a U-2 was shot down over Cuba by two SA-2 Guideline surface-to-air missiles, killing the pilot, Major Rudolf Anderson, Jr. Anderson was posthumously awarded the first Air Force Cross.
In 1963, the CIA started project Whale Tale to develop carrier-based U-2Gs to overcome range limitations. During development of the capability, CIA pilots took off and landed U-2Gs on the aircraft carrier USS Ranger and other ships. The U-2G was used only twice operationally. Both flights occurred from USS Ranger in May 1964 to observe France's development of an atomic bomb test range at Moruroa in French Polynesia.
In early 1964, the Strategic Air Command (SAC) sent a detachment of U-2s from the 4080th to South Vietnam for high-altitude reconnaissance missions over North Vietnam. On 5 April 1965, U-2s from the 4028th SRS (Strategic Reconnaissance Squadron) took photos of SAM-2 sites near Hanoi and Haiphong harbor. On 11 February 1966, the 4080th Wing was redesignated the 100th SRW and moved to Davis-Monthan AFB, Arizona. The SRS detachment at Bien Hoa AB, South Vietnam, was redesignated the 349th SRS.
The only loss of a U-2 during combat operations occurred on 8 October 1966, when Major Leo Stewart, flying with the 349th Strategic Reconnaissance Squadron, developed mechanical problems high over North Vietnam. The U-2 managed to return to South Vietnam where Stewart ejected safely. The U-2 crashed near its base at Bien Hoa. In July 1970, the 349th SRS at Bien Hoa moved to Thailand and was redesignated the 99th SRS, remaining there until March 1976.
In 1969, the larger U-2Rs were flown from the aircraft carrier USS America. The U-2 carrier program is believed to have been halted after 1969. Video of U-2R landing on the USS America in 1969.
In June 1976, the U-2s of the 100th SRW were transferred to the 9th SRW at Beale Air Force Base, California, and merged with SR-71 aircraft operations there. When Strategic Air Command was disestablished in the early 1990s, the wing was transferred to the new Air Combat Command (ACC) and redesignated the 9th Reconnaissance Wing (9 RW).
In 1984, during a major NATO exercise, Royal Air Force Flight Lieutenant Mike Hale intercepted a U-2 at a height of 66,000 feet (20,000 m), where the aircraft had previously been considered safe from interception. Hale climbed to 88,000 feet (27,000 m) in his Lightning F3. 
In 1989, a U-2R of 9 RW, Detachment 5, flying out of Patrick Air Force Base, Florida successfully photographed a space shuttle launch for NASA to assist in identifying the cause of tile loss during launch discovered in the initial post-Challenger missions.
On November 19, 1998, a NASA ER-2 research aircraft set a world record for its weight class (12,000 kilograms (26,000 lb) to 16,000 kilograms (35,000 lb) for an altitude in horizontal flight of 20,479 metres (67,190 ft).
The U-2 is still in frontline service more than 50 years after its first flight despite the advent of surveillance satellites. This is primarily due to the ability to direct flights to objectives at short notice, which satellites cannot do. Production was restarted in the 1980s. The U-2 has outlasted its Mach 3 SR-71 replacement, which was retired in 1998.
 Possible retirement
A two-seat Lockheed U-2 TR-1B
A classified budget document approved by The Pentagon on 23 December 2005 called for the termination of the U-2 program no earlier than 2011, with some aircraft being retired by 2007.
In January 2006, the Secretary of Defense Donald Rumsfeld announced the pending retirement of the U-2 fleet as a cost-cutting measure, and as part of a larger reorganization and redefinition of the Air Force's mission that includes the elimination of all but 56 B-52s and a complete reduction in the F-117 fleet.
Rumsfeld said that this will not impair the Air Force's ability to gather intelligence, which will be done by satellites and a growing supply of unmanned RQ-4 Global Hawk reconnaissance aircraft. However, Congress has not, as of 2009, passed legislation to retire the U-2 as there is no system able to replace it. Proposals to retire the U-2 have been met with significant resistance from military leadership due to gaps in capability that would present if the U-2 were removed from service.
In 2009, the Air Force stated that it plans to extend the U-2 retirement from 2012 until 2014 or later. The delay is to allow more time to field the RQ-4 Global Hawk to replace the U-2.
 Republic of China
Another U-2 operator was the Republic of China (Taiwan), which flew missions mostly over the People's Republic of China (PRC). Since the 1950s, the Republic of China Air Force had used the B-57 aircraft for reconnaissance missions over the PRC, but results were limited by the aircraft's low range and speed. In 1958, ROC and American authorities reached an agreement to create the 5th Squadron, nicknamed the Black Cat Squadron, composed of U-2s.
A total of 27 ROC pilots completed training in the US. In July 1960, the CIA provided the ROC with two U-2s and in December the squadron flew its first mission over mainland China. The objective of the ROC U-2 squadron was to conduct reconnaissance missions assessing the PRC's nuclear capabilities. For this purpose the ROC pilots flew to as far as Gansu and other remote regions in northwest China.
In total, the squadron flew some 100 missions, with five aircraft shot down, including three fatalities and two pilots captured. In 1968, the ROC U-2 fleet was replaced with the newer U-2R. However, with the coming of the Sino-Soviet split and the rapprochement between the US and the PRC, the ROC U-2 squadron stopped entering Chinese airspace, and instead only conducted electronic surveillance over international waters.
During his visit in China in 1972, US President Richard Nixon promised the Chinese authorities to cease all reconnaissance missions over China. This ended the ROC's U-2 operations. In 1974, the two remaining U-2 aircraft in ROC possession were returned to the US.
SAC TR-1A of the 95th Recon Squadron, RAF Alconbury
 Primary list
Sub-section source: Aerospaceweb.org
Initial production, single-seat; 48 built
Two-seat trainer; five built
Enhanced single-seat model with improved engine and modified engine intakes
Enhanced two-seat trainer; unknown built
Enhanced two-seat trainer rebuilt from U-2D airframes with relocation of the seats; six known converted
A-models modified with reinforced landing gear, added arresting hook, and wing spoilers for US Navy carrier operations; three converted
C-models enlarged and improved with underwing pods and increased fuel capacity; 12 built
Enhanced two-seat R-model trainer; one built
Proposed US Navy maritime surveillance R-model; two built
Atmospheric/weather research WU-model
All new "tactical recon" TR-model based on the U-2R with side-looking radar, new avionics, and improved ECM equipment; 33 built
All new two-seat trainer for the TR-1A; two built
Single-seat "earth resource" ER-model for NASA research
New redesignation for the TR-1A; updated with a improved engine, improved sensors, and addition of a GPS system; 31 converted
New redesignated TR-1B two-seat trainer with improved engine; four converted
 U-2E/F details
A Lockheed U-2F being refueled by a Boeing KC-135Q.
In May 1961, in a little-known attempt to extend the U-2's already considerable range, Lockheed modified six CIA U-2s and several USAF U-2s with aerial refueling equipment which allowed the aircraft to receive fuel from either the Boeing KC-97 Stratotanker or from the Boeing KC-135 Stratotanker. This extended the aircraft's range from approximately 4,000 to 8,000 nautical miles (7,400 to 15,000 km) and extended its endurance to more than 14 hours. The J57-powered U-2Bs were re-designated U-2E and the J75-powered U-2Cs were redesignated U-2F. Although the modified U-2s were capable of flying for over 14 hours this took little account of pilot fatigue, and although an additional oxygen cylinder was installed on these aircraft little use was made of this capability. One aircraft was both air-refueling- and carrier-capable and was the only U-2H. 
 U-2R/S details
The U-2R, first flown in 1967, is significantly larger and more capable than the original aircraft. A tactical reconnaissance version, the TR-1A, first flew in August 1981. A distinguishing feature of these aircraft is the addition of a large instrumentation "superpod" under each wing. Designed for standoff tactical reconnaissance in Europe, the TR-1A was structurally identical to the U-2R. The 17th Reconnaissance Wing, Royal Air Force Station Alconbury, England used operational TR-1As from 1983 until 1991. The last U-2 and TR-1 aircraft were delivered to the Air Force in October 1989. In 1992 all TR-1s and U-2s (all U-2Rs) were designated U-2Rs. The two-seat trainer variant of the TR-1, the TR-1B, was redesignated as the TU-2R. After upgrading with the F-118-101 engine, the former U-2Rs were designated the U-2S Senior Year.
 ER-2 details
ER-2#709 takes off from NASA Dryden
A derivative of the U-2 known as the ER-2 (Earth Resources -2) is based at the Dryden Flight Research Center and is used by NASA for high-altitude civilian research including Earth resources, celestial observations, atmospheric chemistry and dynamics, and oceanic processes. Programs using the aircraft include the Airborne Science Program, ERAST and Earth Science Enterprise.
* United States Air Force
o 9th Reconnaissance Wing, Beale Air Force Base, California
+ 1st Reconnaissance Squadron
+ 99th Reconnaissance Squadron
* National Aeronautics and Space Administration, Moffett Federal Airfield, California and Dryden Flight Research Center / Edwards Air Force Base, California
o Additional operational units are operated from various locations around the world as operational requirements demand.
Republic of China (Taiwan)
* Republic of China Air Force
o Black Cat Squadron
 Specifications (U-2S)
Data from International Directory, Global Security, USAF Fact Sheet,
* Crew: One
* Length: 63 ft (19.2 m)
* Wingspan: 103 ft (31.4 m)
* Height: 16 ft (4.88 m)
* Wing area: 1,000 ft² (92.9 m²
* Empty weight: 14,300 lb (6,760 kg)
* Max takeoff weight: 40,000 lb (18,100 kg)
* Powerplant: 1× General Electric F118-101 turbofan, 19,000 lbf (84.5 kN)
* Maximum speed: 434 knots (500 mph, 805 km/h)
* Cruise speed: 373 knots (429 mph, 690 km/h)
* Range: 5,566 nmi (6,405 mi, 10,300 km)
* Service ceiling: 85,000+ ft (25,900+ m)
* Flight endurance: 12 hours