The great majority of supersonic aircraft today are military or experimental aircraft. Most of them, including many military fighter aircraft, are designed to exceed the speed of sound only in certain exceptional flight regimes; a handful of aircraft, such as the SR-71 Blackbird military reconnaissance aircraft and the Concorde supersonic civilian transport, are designed to cruise continuously at speeds above the speed of sound.
Supersonic flight brings with it substantial technical challenges, as the aerodynamics of supersonic flight are dramatically different from those of subsonic flight (i.e., flight at speeds slower than that of sound). These challenges have largely been met. However, political, environmental, and economic obstacles of greater magnitude continue to severely limit the actual deployment of supersonic aircraft, particularly in the civilian world. Additionally, the need and demand for supersonic flight have often been insufficient to justify development or deployment of supersonic aircraft, particularly in the domain of civilian transport. The aforementioned SR-71 and Concorde aircraft are no longer flying today although Concorde was highly profitable in service, but because of the low market among operators (due to sonic booms, relatively high fuel consumption and poor range) in turn making it unprofitable for manufacturers to produce these kinds of aircraft.
Supersonic aircraft usually use low bypass turbofans as they give good efficiency below the speed of sound as well as above, or if extended supercruise is needed turbojet engines are desirable as they give less nacelle drag at supersonic speeds.
A supersonic transport (SST) is a civil aircraft designed to transport passengers at speeds greater than the speed of sound. The only supersonic civilian aircraft to see service are the Soviet produced Tupolev Tu-144 which first flew in 1968 and was retired in 1997, and the Franco-British produced Concorde, which first flew in 1969 and remained in service until 2003. Following the cessation of flying by Concorde in 2003, there are no supersonic civilian aircraft in service.
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