WASHINGTON - Pilots' "automation addiction" has eroded their flying skills to the point that they sometimes don't know how to recover from stalls and other mid-flight problems, say pilots and safety officials. The weakened skills have contributed to hundreds of deaths in airline crashes in the last five years.

Some 51 "loss of control" accidents occurred in which planes stalled in flight or got into unusual positions from which pilots were unable to recover, making it the most common type of airline accident, according to the International Air Transport Association.

"We're seeing a new breed of accident with these state-of-the art planes," said Rory Kay, an airline captain and co-chair of a Federal Aviation Administration advisory committee on pilot training. "We're forgetting how to fly."

Opportunities for airline pilots to maintain their flying proficiency by manually flying planes are increasingly limited, the FAA committee recently warned. Airlines and regulators discourage or even prohibit pilots from turning off the autopilot and flying planes themselves, the committee said.

Fatal airline accidents have decreased dramatically in the U.S. over the past decade. However, The Associated Press interviewed pilots, industry officials and aviation safety experts who expressed concern about the implications of decreased opportunities for manual flight, and reviewed more than a dozen loss-of-control accidents around the world.

Safety experts say they're seeing cases in which pilots who are suddenly confronted with a loss of computerized flight controls don't appear to know how to respond immediately, or they make errors - sometimes fatally so.

A draft FAA study found pilots sometimes "abdicate too much responsibility to automated systems." Because these systems are so integrated in today's planes, one malfunctioning piece of equipment or a single bad computer instruction can suddenly cascade into a series of other failures, unnerving pilots who have been trained to rely on the equipment.

The study examined 46 accidents and major incidents, 734 voluntary reports by pilots and others as well as data from more than 9,000 flights in which a safety official rides in the cockpit to observe pilots in action.

It found that in more than 60 percent of accidents, and 30 percent of major incidents, pilots had trouble manually flying the plane or made mistakes with automated flight controls.

A typical mistake was not recognizing that either the autopilot or the auto-throttle - which controls power to the engines - had disconnected. Others failed to take the proper steps to recover from a stall in flight or to monitor and maintain airspeed.

The airline industry is suffering from "automation addiction," Kay said.

In the most recent fatal airline crash in the U.S., in 2009 near Buffalo, N.Y., the co-pilot of a regional airliner programmed incorrect information into the plane's computers, causing it to slow to an unsafe speed. That triggered a stall warning. The startled captain, who hadn't noticed the plane had slowed too much, responded by repeatedly pulling back on the control yoke, overriding two safety systems, when the correct procedure was to push forward.

An investigation later found there were no mechanical or structural problems that would have prevented the plane from flying if the captain had responded correctly. Instead, his actions caused an aerodynamic stall. The plane plummeted to earth, killing all 49 people aboard and one on the ground.

Two weeks after the New York accident, a Turkish Airlines Boeing 737 crashed into a field while trying to land in Amsterdam. Nine people were killed and 120 injured. An investigation found that one of the plane's altimeters, which measures altitude, had fed incorrect information to the plane's computers.

That, in turn, caused the auto-throttle to reduce speed to a dangerously slow level so that the plane lost lift and stalled. Dutch investigators described the flight's three pilots' "automation surprise" when they discovered the plane was about to stall. They hadn't been closely monitoring the airspeed.

Last month, French investigators recommended that all pilots get mandatory training in manual flying and handling a high-altitude stall. The recommendations were in response to the 2009 crash of an Air France jet flying from Brazil to Paris. All 228 people aboard were killed.

An investigation found that airspeed sensors fed bad information to the Airbus A330's computers. That caused the autopilot to disengage suddenly and a stall warning to activate.

The co-pilot at the controls struggled to save the plane, but because he kept pointing the plane's nose up, he actually caused the stall instead of preventing it, experts said. Despite the bad airspeed information, which lasted for less than a minute, there was nothing to prevent the plane from continuing to fly if the pilot had followed the correct procedure for such circumstances, which is to continue to fly levelly in the same direction at the same speed while trying to determine the nature of the problem, they said.

In such cases, the pilots and the technology are failing together, said former US Airways Capt. Chesley "Sully" Sullenberger, whose precision flying is credited with saving all 155 people aboard an Airbus A320 after it lost power in a collision with Canada geese shortly after takeoff from New York's LaGuardia Airport two years ago.

"If we only look at the pilots - the human factor - then we are ignoring other important factors," he said. "We have to look at how they work together."

The ability of pilots to respond to the unexpected loss or malfunction of automated aircraft systems "is the big issue that we can no longer hide from in aviation," said Bill Voss, president of the Flight Safety Foundation in Alexandria, Va. "We've been very slow to recognize the consequence of it and deal with it."

The foundation, which is industry supported, promotes aviation safety around the world.

Airlines are also seeing smaller incidents in which pilots waste precious time repeatedly trying to restart the autopilot or fix other automated systems when what they should be doing is "grasping the controls and flying the airplane," said Bob Coffman, another member of the FAA pilot training committee and an airline captain.

Paul Railsback, operations director at the Air Transport Association, which represents airlines, said, "We think the best way to handle this is through the policies and training of the airlines to ensure they stipulate that the pilots devote a fair amount of time to manually flying. We want to encourage pilots to do that and not rely 100 percent on the automation. I think many airlines are moving in that direction."

In May, the FAA proposed requiring airlines to train pilots on how to recover from a stall, as well as expose them to more realistic problem scenarios.

But other new regulations are going in the opposite direction. Today, pilots are required to use their autopilot when flying at altitudes above 24,000 feet, which is where airliners spend much of their time cruising. The required minimum vertical safety buffer between planes has been reduced from 2,000 feet to 1,000 feet. That means more planes flying closer together, necessitating the kind of precision flying more reliably produced by automation than human beings.

The same situation is increasingly common closer to the ground.

The FAA is moving from an air traffic control system based on radar technology to more precise GPS navigation. Instead of time-consuming, fuel-burning stair-step descents, planes will be able to glide in more steeply for landings with their engines idling. Aircraft will be able to land and take off closer together and more frequently, even in poor weather, because pilots will know the precise location of other aircraft and obstacles on the ground. Fewer planes will be diverted.

But the new landing procedures require pilots to cede even more control to automation.

"Those procedures have to be flown with the autopilot on," Voss said. "You can't afford a sneeze on those procedures."

Even when not using the new procedures, airlines direct their pilots to switch on the autopilot about a minute and a half after takeoff when the plane reaches about 1,000 feet, Coffman said. The autopilot generally doesn't come off until about a minute and a half before landing, he said.

Pilots still control the plane's flight path. But they are programming computers rather than flying with their hands.

Opportunities to fly manually are especially limited at commuter airlines, where pilots may fly with the autopilot off for about 80 seconds out of a typical two-hour flight, Coffman said.

But it is the less experienced first officers starting out at smaller carriers who most need manual flying experience. And, airline training programs are focused on training pilots to fly with the automation, rather than without it. Senior pilots, even if their manual flying skills are rusty, can at least draw on experience flying older generations of less automated planes.

Adding to concerns about an overreliance on automation is an expected pilot shortage in the U.S. and many other countries. U.S. airlines used to be able to draw on a pool of former military pilots with extensive manual flying experience. But more pilots now choose to stay in the armed forces, and corporate aviation competes for pilots with airlines, where salaries have dropped.

Changing training programs to include more manual flying won't be enough because pilots spend only a few days a year in training, Voss said. Airlines will have to rethink their operations fundamentally if they're going to give pilots realistic opportunities to keep their flying skills honed, he said.

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