Who is really flying a modern airliner, the pilot or the computer?

A modern airliner is flown by both, and the split of work is the point. On a fly-by-wire aircraft the pilot's stick or yoke no longer moves cables to the control surfaces. The movements are converted to electronic signals, and flight control computers decide how to move each control surface to give the ordered response. The computers stabilise the aircraft without the pilot's involvement and try to prevent the pilot from operating outside the aircraft's safe performance envelope.

The autopilot is the older partner. It controls the aircraft's path without constant intervention from a human operator, but it does not replace the humans: it lets them focus on broader aspects such as the trajectory, the weather and on-board systems. The first gyroscopic autopilot was built by Sperry in 1912, and in 1914 Lawrence Sperry showed it off in Paris by flying with his hands away from the controls, in full view of onlookers.

Fly-by-wire came to airliners later. The Airbus A320 began service in 1988 as the first mass-produced airliner with digital fly-by-wire controls. Since the loss of all flight control computers would make an aircraft uncontrollable at once, such systems use redundant computers or a mechanical or hydraulic backup.

The hardest moments are when the automation steps back. On 1 June 2009, Air France Flight 447, an Airbus A330, crashed into the Atlantic, killing all 228 on board. Investigators concluded that ice crystals likely blocked its pitot tubes, so the speed readings were inconsistent and the autopilot disconnected. The crew reacted incorrectly, and the aircraft entered a stall that the pilots failed to correct. The lesson is that a good partnership needs the human to know exactly what the machine is, and is not, doing.