The Grumman X-29 experimental aircraft was deliberately designed to be unstable in flight. That configuration gave it greater agility, but also meant that a human pilot could not control the craft without assistance from an on-board computer. For safety reasons, the X-29 used three, identical, digital computers, any one of which could assist the pilot.

At the time, some criticized the concept of fly-by-wire and the inherently unstable design, and the fact that if the computer failed the X-29 would crash instantly. But in a long series of test flights beginning in 1984, the computers worked well and the X-29 completely validated the concept. Fly-by-wire has been employed in a variety of civil and military aircraft since then.