Four prototypes of the B-1A Mach 2.2 strategic bomber were developed and tested in the mid-1970s, but the program was canceled in 1977 before going into production
The cool photo in this post shows B-1A tail number 76-0174 which actually is B-1A No.4.
On Aug. 6, 1980 this aircraft completed an 11-hour sortie which at the time was the longest nonstop flight logged by a B-1.
First flown in February 1979, the USAF primarily used 76-0174 as the avionics test bed for the B-1B Program. Unlike the other B-1As which had crew escape modules, this aircraft had ejection seats (standard on the B-1B).
Today this aircraft is on display at the Strategic Air Command & Aerospace Museum near Offutt Air Force Base (AFB) in Nebraska.
The B-1A was initially developed in the 1970s as a replacement for the B-52. Four prototypes of this long-range, high speed (Mach 2.2) strategic bomber were developed and tested in the mid-1970s, but the program was canceled in 1977 before going into production. Flight testing continued through 1981.
The B-1B is an improved variant initiated by the Reagan administration in 1981. Major changes included and additional structure to increase payload by 74,000 pounds, an improved radar and reduction of the radar cross-section (RCS) by an order of magnitude. The inlet was extensively modified as part of this RCS reduction, necessitating a reduction in maximum speed to Mach 1.2.
The first production B-1 flew in October 1984, and the first B-1B was delivered to Dyess AFB, Texas, in June 1985. Initial operational capability (IOC) was achieved on Oct. 1, 1986. The final B-1B was delivered May 2, 1988.
The B-1B holds almost 50 world records for speed, payload, range, and time of climb in its class. The National Aeronautic Association recognized the B-1B for completing one of the 10 most memorable record flights for 1994. The most recent records were made official in 2004.

Photo credit: Edwards History Office file photo / U.S. Air Force
Artwork courtesy of AircraftProfilePrints.com
Source: U.S. Air Force