America Spent $1.5 Billion On A Mach 3 Bomber. It Became A Research Plane Instead.

The B-70 Valkyrie was designed to be America's Mach 3 bomber. After $1.5 billion spent, it never carried a weapon and became a research plane instead. North American Aviation began developing the B-70 in 1957 as a Mach 3 intercontinental nuclear bomber to replace the B-52. President Kennedy canceled the bomber program in March 1961 after approximately $800 million had been spent, but two prototypes were completed as the XB-70 Valkyrie. The aircraft flew from 1964 to 1969, logging 129 flights but only 1 hour and 48 minutes at Mach 3; one was lost in a mid-air collision with an F-104 in June 1966. Built of brazed stainless steel to survive 630-degree temperatures at cruise speed, it used six General Electric J93 engines and an unconventional delta wing design with folding tips. The surviving aircraft is now displayed at the National Museum of the United States Air Force in Dayton, Ohio.