In nearly 100 million flights by United States airlines over the past decade, there has been a single fatality. Other than most landings and takeoffs, the planes have largely been flying themselves.
But the recent crashes of Boeing 737 Max 8 jets in Indonesia and Ethiopia have raised questions about the downside of all that automation.
Pilots now spend more time learning these automated systems than practicing hands-on flying, so newer pilots are less comfortable with taking manual control when the computer steers them wrong, according to interviews with a dozen pilots and pilot instructors at major airlines and aviation universities around the world.
“The automation in the aircraft, whether it’s a Boeing or an Airbus, has lulled us into a sense of security and safety,” said Kevin Hiatt, a former Delta Air Lines pilot who later ran flight safety for JetBlue. Pilots now rely on autopilot so often, “they become a systems operator rather than a stick-and-rudder pilot.”
As a result, he said, “they may not exactly know or recognize quickly enough what is happening to the aircraft, and by the time they figure it out, it may be too late.”
In October, a Lion Air jet crashed in Indonesia, killing 189 people. Investigators now think the pilots struggled to control the Boeing aircraft after its automated systems malfunctioned, in part because they didn’t fully understand how the automation worked. The authorities are investigating what caused Sunday’s crash of the same model jet in Ethiopia, in which 157 people died.
While automation has contributed to the airline industry’s stellar safety record in recent years, it has also been a factor in many of the crashes that have still occurred around the world. A 2011 study by a federal task force found that in about 60 percent of 46 recent accidents, pilots had trouble manually flying the plane or handling the automated controls. Complicated automation systems can also confuse pilots and potentially cause them to take action they shouldn’t, pilots said.
President Trump weighed in on Tuesday, posting on Twitter that airplanes have become too technologically complex and that he wants “great flying professionals that are allowed to easily and quickly take control of a plane!”
Overdependence on automation has been an issue for decades. A 1997 American Airlines pilot-training video warned that the problem was well known among pilots. In 2013, a federal task force concluded in a 267-page report that pilots relied too often on automation and should be required to improve their manual flying skills. That same year, investigators found that the pilots over-relied on automation in the 2013 crash of an Asiana Airlines jet in San Francisco that left three dead.
In recent years, the Federal Aviation Administration has advised airlines to encourage pilots to fly manually when appropriate, among other policies intended to improve manual skills.
“A specific focus of our efforts has been ensuring that our pilots have the manual handling skills and confidence to take control of the aircraft if the automation does not perform as expected,” an F.A.A. spokesman said in an email.
Yet the agency moves slowly. This week, the F.A.A. finally began enforcing a rule it announced about six years ago requiring pilots to practice in simulators how to handle stalls, a situation in which a plane loses lift. The rule was enacted in response to a 2009 crash.
In 2016, the Transportation Department’s Office of Inspector General issued a report that found the F.A.A. had not ensured that airlines adequately trained pilots in hands-on flying or on how to monitor a plane on autopilot. The report also found the agency did not track how often pilots flew manually.
A decade ago, Chesley B. Sullenberger III, landed a US Airways jet with 155 people aboard in the Hudson River. That represents to many pilots the sort of manual intervention that is sometimes necessary.
“Hopefully, we’ll do something before we begin to have a litany of recent fatal accidents,” Mr. Sullenberger said in a recent interview. “It could happen tomorrow. It could happen next year. I can’t say. But I think it’s inevitable if we continue down this path.”
The issue has become more acute in recent years as aircraft have become more automated and a global pilot shortage has forced carriers to fill their cockpits with less experienced pilots, particularly in emerging markets. At the same time, the stream of military aviators that the big carriers have long relied on is dwindling.
The most seasoned pilots are aging out of the profession — they are required to retire at age 65 in the United States — and many said their successors might now know how to handle the unexpected.
“There’s nothing wrong with the millennials; they’re really sharp and hungry for the information,” said Shem Malmquist, a Boeing 777 captain and visiting professor at the Florida Institute of Technology’s College of Aeronautics. “We’re not exposing them — we’re not giving them the chance to get the information.”
Karlene Petitt, an international airline pilot who wrote a Ph.D. dissertation about pilot training at Embry-Riddle Aeronautical University, said the new training regimen was producing less well-rounded pilots.
“They can punch the buttons, but will they be able to fly that airplane when it breaks?” she asked.
Mr. Sullenberger noted that flight schools, where much of the manual training takes place, were limited because some insurers restricted how much flying students could do in poor visibility.
“They may have never flown in a cloud before,” he said.
Kit Darby, a former United Airlines captain and Boeing flight instructor who now trains pilots at another large carrier, said training for passenger pilots remained exhaustive and still focused on manual skills, including 1,500 hours of flight time and nearly 30 days in simulators. The bigger problem, he said, is the degradation of those skills once pilots get into the cockpit of an advanced passenger jet and begin to rely on autopilot.
Many airlines encourage pilots to avoid automation when they can, he said, and annual reviews still test their manual skills. “When it’s a beautiful day, we want you to turn the automation off,” he said.
Mr. Darby and others said airlines in emerging markets were especially reliant on automation. Mr. Darby, who is also a career consultant for young pilots, said those markets had more acute pilot shortages, forcing carriers to rely on automation to cover up some of their aviators’ lack of experience. In the Ethiopian Airlines crash this week, one of the pilots had just 200 hours of flight time, less than a seventh of the time the F.A.A. generally requires to fly a passenger plane.
After the 2013 Asiana crash, the National Transportation Safety Board found that the carrier “emphasized the full use of all automation and did not encourage manual flight.” If the airline allowed pilots to fly manually more often, the pilot most likely would have prevented the crash, the agency said.
Dennis Tajer, an American Airlines captain and a spokesman for the airline’s pilots’ union, said Boeing and Airbus had encouraged that sort of reliance on automation by pitching their planes to carriers as capable of being flown by lesser-trained pilots.
“We’ve seen insidious marketing of aircraft to accommodate less experienced and perhaps a lower grade of pilot,” he said.
Boeing and Airbus did not immediately respond to requests for comment.
Not all pilots are as worried. Some said the advances in safety from automation outweighed any added risks.
“The data is there that we’ve got a good system,” said David Williams, a former F.A.A. inspector. “The reduction of training is overridden by the advances in the equipment.”