When was the Blackbird stealth jet invented?

Answer 1

The Blackbird was not stealth! The concept of stealth did not exist at the time it was designed and built.

Initial work on it began in the spring of 1958 at the request of the CIA as a replacement (A-12) for the earlier, very slow U-2. The first test flight was in April 1962 from Area 51 in Nevada. It went into actual use in 1966.

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The original concept was for the A-12 reconnaissance aircraft for the CIA (Project Oxcart), for which design began in the late 1950s. The USAF was seeking a Mach 3+ interceptor and ordered 3 AF-12 variants in 1960. The designation was the YF-12A.

The A-12 first flew on April 26, 1962.

The YF-12A (crew of two) first flew on August 7, 1963.

When the F-12 program was scaled back, the longer variant of the A-12 was proposed as a strategic bomber, the B-71. 32 of these aircraft were built as RS-71 twin-crew reconnaissance aircraft, with the designation soon changed to SR-71. The SR-71 first flew on December 22, 1964. Production ceased in 1968.