Lockheed Martin has begun work on a successor to the supersonic Blackbird SR-71 spy plane.
The unmanned SR-72 will use an engine that combines a turbine and a ramjet to reach its top speed of Mach 6 – about 3,600mph (5,800km/h).
Like its predecessor, the SR-72 will be designed for high-altitude surveillance but might also be fitted with weapons to strike targets.
Lockheed said the aircraft should be operational by 2030.
The SR-72 is being developed at Lockheed Martin’s Skunk Works R&D centre in California that designed and built the original Blackbird.
That aircraft first flew in 1964 and was a mainstay of US Air Force spying and surveillance work until 1998. It typically flew at altitudes of 24,000m (80,000ft) and could reach speeds of Mach 3.
In a blogpost about the SR-72, Lockheed Martin said the aircraft would operate at similar altitudes but would fly far faster. At Mach 6 the plane could travel the 3,500 miles (5,500km) from New York to London in less than an hour.
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