NASA could bring back SR-71 as missing Blackbird sparks wild speculation about the world's fastest plane ever and former staffers contacted for 'help'
SR-72: US secret hypersonic jet to allegedly break sound barrier in 2025 | Believed to be a top-secret project of the US Air Force, the SR-72 is touted to reach over 4,000 mph (6,437 kph), making it the fastest plane ever developed.
