X-29 in flight

You don't see many aircraft that look like the X-29, and for good reason--it's exceedingly hard to keep them stable. But using a computerized fly-by-wire system (in which electronic controls replace mechanical ones) and incorporating composite materials, the X-29 became, in NASA's precise phrasing, "the first forward-swept-wing airplane in the world to exceed Mach 1 in level flight."

The two Grumman-built X-29 aircraft flew from 1984 to 1992, making more than 400 total flights. This photo shows smoke generators at work, providing visual feedback to researchers about airflow over the X-Plane. The tufts along the fuselage and wings perform a similar function.