Lockheed SR-71 Blackbird SR-71B

The SR-71B was the programme's two-seat trainer, and only two were built: 61-7956 and 61-7957. It replaced the reconnaissance systems officer's station with a second, instructor's cockpit raised above the student's, so that both crew members kept a good field of view; to offset the aerodynamic effect of that raised canopy, the trainers carried two small titanium ventral strakes under each engine nacelle, a detail shared with the SR-71C.

The trainer fleet was halved on 11 January 1968, when 61-7957 was lost on approach after a double generator failure followed by a double flameout; the crew ejected safely. The loss forced the construction of a replacement assembled from other airframes, the SR-71C.

The survivor had a remarkably long career: it flew its 1,000th sortie on 15 January 1982 and, after military retirement, was officially delivered to NASA's Dryden Flight Research Center on 25 July 1991 as NASA 831. There it served both as a research platform and as the crew proficiency aircraft until October 1997. It is preserved today at the Air Zoo in Michigan.