The U-2 is a high-altitude reconnaissance aircraft that flies above 65,000 feet. Although it is not air-refuelable, the U-2 can remain airborne for more than twelve hours. Missions normally do not exceed nine hours.
KNOWN VARIANTS
U-2A First production one-seat reconnaissance model; 48 built
U-2B Two-seat trainer; 5 built
U-2C Improved one-seat reconnaissance model with a new engine and modified engine inlets
U-2D Two-seat trainer
U-2CT Two-seat trainer rebuilt from U-2D airframes but with the training pilot seated at a higher level; at least 6 converted
U-2G U-2A models modified with stronger landing gear, an arresting hook, and wing spoilers in order to operate from US Navy aircraft carriers; 3 converted but rarely used
U-2R Enlarged and improved U-2C with underwing pods and increased fuel capacity; 12 built
U-2RT Two-seat trainer based on U-2R; 1 built
U-2EPX Proposed maritime surveillance model for the US Navy based on the U-2R; 2 built but not put into service
WU-2 Research aircraft used by the US Air Force for atmospheric research
TR-1A Improved U-2R with side-scanning radar, new avionics, and improved ECM equipment; 33 built
TR-1B Two-seat trainer for the TR-1A; 2 built
ER-2 One-seat "earth resource" research aircraft built for NASA
U-2S New designation for the TR-1A; also updated with a more efficient engine, improved sensors, and the addition of a GPS system; 31 converted
U-2ST Redesignated U-2R/TR-1B two-seat trainer with updated engine; 4 converted
