SR-71: The Complete Illustrated History of the Blackbird, The World's ... - Richard H. Graham - Google Books

https://books.google.de/books?id=RVexgTUqPw4C&pg=PA147&lpg=PA147&dq=sr-71+radar+recording+area&source=bl&ots=_ssgeMaEkF&sig=oHRV

 At the height of the Cold War in 1964, President Johnson announced a new aircraft dedicated to strategic reconnaissance. The Lockheed SR-71 Blackbird spy plane flew more than three-and-a-half times the speed of sound, so fast that no other aircraft could…