The cause of last month’s fatal plane crash in South Korea has yet to be determined, but it has thrown the spotlight on a subject little understood by the general public: how planes are maintained.
Jeju Air, the airline that operated the flight that killed 179 people, said pre-flight checks did not raise concerns and the plane, a Boeing 737-800 that was about 15 years old, had no history of accidents.
While there is no evidence that poor maintenance played a role in the crash, experts say the plane’s repair history, which includes work done by maintenance companies in other countries, will be an important part of the crash investigation, as it usually is.
Here’s what you should know about how aircraft are maintained.
The basics
Airline executives, pilots, mechanics, regulators and others have vital and overlapping roles in the care of commercial jets.
On the front line is a practice that will be familiar to many passengers even if they don’t know its name: line maintenance, which includes regular inspections and repairs between flights. Before a jet takes off, pilots perform visual and other inspections for damage or other problems. Aircraft mechanics also perform periodic checks. A mechanic can often quickly fix the problem, fix it, or safely patch it until the problem is fixed at a later date. Serious problems can lead to long delays or cancellations.
In addition, every part of the plane, down to the nuts and bolts, undergoes routine inspections, repairs or replacements. These checks are usually scheduled based on how many hours the aircraft has been used, the number of flights, the weather, or some combination of these factors. These inspections are overseen by aviation authorities around the world, and many follow the guidelines of regulators at the Federal Aviation Administration or its European Union partner.
When it comes to more intensive maintenance that could take a plane out of service for days or weeks, the world’s largest airlines do most of the work themselves. Some, including Lufthansa and Delta Air Lines, even sell these services to others. But every airline outsources at least some of its work to companies that make parts and aircraft, such as Boeing and Airbus, or to third parties. Small carriers are particularly dependent on practice.
“If you look at the long tail of aircraft operators, most of them are very small, so it never made sense for them to invest capital,” said Jonathan Berger, founder of Alton Aviation, a consulting firm. “Outsourcing has been around since time immemorial.”
The rise of outsourcing
Although it has always played a role in aviation, outsourcing has accelerated in recent decades. In the United States, the share of outsourced aircraft maintenance spending more than doubled from 1990 to 2011, rising from about 20 percent to more than 44 percent, according to a 2012 Congressional Research Service report. Airlines typically do not publish such spending, and few outside the industry track or estimate it.
Worldwide, airlines still perform almost all of their line maintenance. But they often send more extensive work to companies specializing in aircraft maintenance, repair and overhaul. This work is usually divided into three categories, covering the structure of the aircraft – or the body, wings and tail – the engine and various other components.
Labor makes up most of the cost of maintaining an airplane’s structure, so airlines in wealthier countries often send that work to countries where wages are lower. Some US airlines send planes to El Salvador, for example, and Western European carriers send them to Eastern Europe.
With engines, materials make up the bulk of repair costs, so outsourcing to lower-income countries doesn’t save airlines that much. However, much of this work is also outsourced, often to engine manufacturers, because repairing these large machines is expensive and complex, according to Mr. Berger. Most jet engines for large commercial aircraft are manufactured by several American and European companies.
The global network of maintenance service providers is a growing market estimated at more than 100 billion dollars. Proponents say it allows airlines, especially low-cost carriers, to plan costs and focus on what they do best: efficiently plan, sell and manage flights. Airlines also benefit because they can turn to experts who can focus on specific types of maintenance or aircraft.
Is outsourcing safe?
Many aviation industry experts say outsourcing is safe and necessary, and note that the FAA still oversees maintenance of American aircraft wherever it occurs. But some consumer groups and labor unions representing American mechanics have expressed concern about it.
“There is a quality problem, and the industry’s denial is just a lie,” said William J. McGee, who has spent decades advocating for travelers to lawmakers and regulators and is a senior fellow at the American Economic Liberties Project, a progressive group.
In the 2000s and early 2010s, the Chief Inspector of the Department of Transport investigated the FAA’s oversight of foreign and domestic service stations and found it missing. Aircraft mechanics reported finding obvious faults in aircraft returning from overseas service. And their unions, including the International Brotherhood of Teamsters and the Transportation Workers Union, have expressed concern that workers abroad are not held to the same rigorous standards as those in the United States.
The FAA has recently addressed some of these issues. This month, a new agency rule will begin requiring foreign services to conduct drug and alcohol tests on employees who perform certain security maintenance, affecting as many as 977 locations in 65 countries.
“This rule will ensure that these employees are held to the same high level of safety standards, regardless of where they are physically located,” Mike Whitaker, outgoing FAA administrator, he said in a statement last month.
Outsourcing advocates say oversight by airlines and the FAA is rigorous today, noting that despite several shocking accidents and incidents, flying commercial aircraft is far safer than other common modes of travel, including cars, buses or trains.
Maintenance needs are growing
Despite a significant slowdown at the start of the pandemic, air travel has rebounded much faster than the industry expected. Airlines are now eager to expand and upgrade their fleets.
But Boeing and Airbus, the two major jet makers, have struggled to produce planes. Boeing has had to slow production in recent years, first after two fatal crashes of its most popular plane, the 737 Max, in 2018 and 2019. It was forced to do so again last year after the commission blew up a Max jet in flight, and in the fall it largely shut down Max production during a seven-week strike.
Airlines also had to pull Airbus jets out of service to carry out unexpected inspections of Pratt & Whitney engines after the engine maker discovered a quality flaw. Airbus and Boeing are also struggling with lingering problems from the pandemic period, including shortages of parts and skilled workers.
The slow delivery of new aircraft has forced airlines to use older aircraft for longer, which is safe but often requires more maintenance. The newer engines, which are packed with new technology that makes them more efficient, also required more repairs and maintenance than expected.
But the number of people wanting a career in aircraft maintenance lags behind demand.
“It’s not just the airlines that are hiring, but general aviation is hiring, corporate aviation is hiring,” said Chuck Horning, professor of aircraft maintenance at Embry-Riddle Aeronautical University, referring to the planes that many companies use to transport people and goods. “And then you have industries that didn’t really exist when I graduated in 1986, like the aerospace industry and unmanned aerial systems.”
