Lockheed U-2 U-2D

The U-2D was not new-build but a rebuild of U-2A airframes: the large camera bay behind the pilot made way for a second crew station and equipment designed to measure the infrared emissions of aircraft and missiles. The aim was not to photograph foreign territory but to establish whether a satellite could detect a missile launch by its thermal signature and so give early warning of a Soviet nuclear attack. The variant kept the programme's original Pratt & Whitney J57-P-13B turbojet and never received the J75 upgrade that transformed most of the fleet.

The only U-2D left in the world is displayed at the Blackbird Airpark in Palmdale, California — an annex of the Air Force Flight Test museum at Edwards dedicated on 27 September 1991 — alongside an SR-71A, an A-12 and a D-21 drone. It is serial 56-6721, known internally as Article 388: the forty-eighth U-2 airframe built and the twenty-eighth U-2A completed at Lockheed's Oildale plant in California.

Delivered in October 1957 to the 4080th Strategic Reconnaissance Wing at Laughlin AFB, Del Rio, Texas, the aircraft was at the centre of the episode remembered as the "Miracle at Cortez" on 3 August 1959: during a training flight, Taiwanese pilot Maj. Mike Hua suffered a flame-out at 70,000 ft and dead-sticked the aeroplane onto Cortez, Colorado, in a belly landing that damaged but saved both pilot and airframe.

It was during that repair that the aircraft was modified to carry a second crewman and an infrared sensor suite, and was redesignated U-2D. Delivered to Edwards AFB in December 1959, it was assigned to the Special Projects Branch of the 6512th Test Group and flew in Projects LOW CARD and SMOKEY JOE, supporting development of the missile detection and alarm satellite system.

In May 1968 it received new instrumentation for a series of 31 test sorties under Program 949, a space-borne missile warning system; the flights, staged from Hanscom AFB, Massachusetts and Patrick AFB, Florida, continued through October of that year. During the 1970s the same aircraft served as chase plane for COMPASS COPE unmanned vehicles, and students at the Air Force Test Pilot School at Edwards occasionally flew it as part of their course.

56-6721 was retired in 1980 and displayed at the March Field Museum in Riverside, California until 1996. It then went to Lockheed Martin's facility at Air Force Plant 42 for restoration and, since November 2001, has stood on show at the Blackbird Airpark in Palmdale.