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American Airlines resumes Boeing 737 Max flights

After two crashes killed 346 people, the Boeing 737 Max is back in service in the US and Brazil. Plus: Everything you need to know about the plane's other issues.

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Two Boeing 737 Max 8s crashed, killing 346 people.

Boeing

American Airlines put the Boeing 737 Max back into passenger service in the US on Tuesday when it operated a 737 Max 8 between Miami International Airport and New York's LaGuardia Airport. The flight, which landed in New York at 1:12 p.m. ET after flying almost three hours, comes 21 months after the Max was grounded over a pair of crashes in 2018 and 2019 that killed 346 people. 

The American flight follows the Federal Aviation Administration's decision last month to clear the beleaguered aircraft to return to the sky. As part of the decision the agency has ordered Boeing and airlines to make repairs to a flight control system blamed for both crashes and increase pilot training. Other reports have identified additional concerns with the airliner's flight control computerwiring and engines

The Max has also resumed carrying passengers in Brazil, and other US airlines that fly the Max are planning to add the Max back into their fleets by the second quarter of next year. Aviation safety agencies in Canada and the European Union are still conducting their own reviews of the plane. Until those are completed, the 737 Max will remain grounded in those places.

The crashes and the aircraft's grounding have been a huge blow to Boeing, which has thousands of 737 Max orders on its books. Even once it's flying again worldwide, the company will have to work vigorously to retain the trust of airlines and the flying public for the Max family. Here's everything else we know about the airliner so far. 

What happened in the two crashes?

In the first crash, on Oct. 29, 2018, Lion Air flight 610 dove into the Java Sea 13 minutes after takeoff from Jakarta, Indonesia, killing 189 people. The flight crew made a distress call shortly before losing control. That aircraft was almost brand-new, having arrived at Lion Air three months earlier. 

The second crash occurred on March 10, 2019 when Ethiopian Airlines flight 302 departed Addis Ababa Bole International Airport bound for Nairobi, Kenya. Just after takeoff, the pilot radioed a distress call and was given immediate clearance to return and land. But before the crew could make it back, the aircraft crashed 40 miles from the airport, six minutes after it left the runway. Aboard were 149 passengers and eight crew members. The aircraft involved was only four months old. 

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The 737 Max 9, shown here at the 2016 Paris Air Show, is a larger version of the Max 8, but with the same piloting system that's under investigation.

Kent German/CNET

What caused the crashes?

Planes crashed rarely have a single cause, which is the case here. On Oct. 25, 2019, the Indonesian National Transportation Safety Committee published its final report on the Lion Air crash. The report identifies nine factors that contributed to the crash, but largely blames MCAS. Before crashing, the Lion Air pilots were unable to determine their true airspeed and altitude and they struggled to take control of the plane as it oscillated for about 10 minutes. Each time they pulled up from a dive, MCAS pushed the nose down again. 

"The MCAS function was not a fail-safe design and did not include redundancy," the report said. Investigators also found that MCAS relied on only one sensor, which had a fault, and flight crews hadn't been adequately trained to use the system. Improper maintenance procedures, confusion in the cockpit and the lack of a cockpit warning light (see next question) contributed to the crash, as well.

On March 9, 2020, almost one year to the day since the crash in Addis Ababa, Ethiopia's Aircraft Accident Investigation Bureau published an interim analysis. Like the Indonesian findings, it cites design flaws with MCAS such its reliance on a single angle-of-attack sensor. It also blamed Boeing for providing inadequate training to crew on using the Max's unique systems. (The Seattle Times has a great deep dive on the report.)

Unlike their Indonesian counterparts, the Ethiopian investigators do not mention maintenance problems with the plane nor does it blame the flight crew. "The aircraft has a valid certificate of airworthiness and maintained in accordance with applicable regulations and procedures," the report said. "There were no known technical problems before departure." 

Until Ethiopia releases another report, remember that crash investigations are tremendously complex -- it takes months to evaluate the evidence and determine a probable cause. Investigators must examine the debris, study the flight recorders and, if possible, check the victims' bodies to determine the cause of death. They also involve multiple parties including the airline, the airplane and engine manufacturers, and aviation regulatory agencies.

What is the Boeing 737 Max?

Built to compete with the Airbus A320neo, the 737 Max is a family of commercial aircraft that consists of four models. The Max 8, which is the most popular version, made its first flight on Jan. 29, 2016, and entered passenger service with Malaysia's Malindo Air on May 22, 2017. (Malindo no longer flew the plane by the time of the first crash.) Seating between 162 and 210 passengers, depending on the configuration, it's designed for short- and medium-haul routes, but also has the range (3,550 nautical miles, or about 4,085 miles) to fly transatlantic and between the mainland US and Hawaii. The larger Max 9 first flew in 2017, and the Max 10 has yet to fly (it made its formal debut Nov. 22, 2019). The smaller 737 Max 7 flew for the first time in May 2018.

The design of the 737 Max series is based on the Boeing 737, an aircraft series that has been in service since 1968. As a whole, the 737 family is the best-selling airliner in history. At any given time, thousands of some version of it are airborne around the world and some airlines, like Southwest and Ryanair, have all-737 fleets. If you've flown even occasionally, you've most likely flown on a 737.

What's different about the 737 Max series compared with earlier 737s?

The 737 Max can fly farther and carry more people than the previous generation of 737s, like the 737-800 and 737-900. It also has improved aerodynamics and a redesigned cabin interior and flies on bigger, more powerful and more efficient CFM LEAP engines. CFM is a joint venture between General Electric and France's Safran.

Those engines, though, required Boeing to make critical design changes. Because they're bigger, and because the 737 sits so low to the ground (a deliberate 737 design choice to let it serve small airports with limited ground equipment), Boeing moved the engines slightly forward and raised them higher under the wing. (If you place an engine too close to the ground, it can suck in debris while the plane is taxiing.) That change allowed Boeing to accommodate the engines without completely redesigning the 737 fuselage -- a fuselage that hasn't changed much in 50 years.

But the new position of the engines changed how the aircraft handled in the air, creating the potential for the nose to pitch up during flight. A pitched nose is a problem in flight -- raise it too high and an aircraft can stall. To keep the nose in trim, Boeing designed software called the Maneuvering Characteristics Augmentation System, or MCAS. When a sensor on the fuselage detects that the nose is too high, MCAS automatically pushes the nose down. (For background on MCAS, read these excellent in-depth stories from The Air Current and The Seattle Times.) 

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Compared with previous versions of the 737, the Max's engines sit farther forward and higher up on the underwing pylons.

Andrew Hoyle/CNET

When was the Max grounded?

About 30 airlines operated the Max by the time of the second crash (the three largest customers being Southwest Airlines, American Airlines and Air Canada). Most of them quickly grounded their planes a few days later. Besides the airlines already mentioned that list includes United Airlines, WestJet, Aeromexico, Aerolíneas Argentinas, GOL Linhas Aéreas, Turkish Airlines, FlyDubai, Air China, Copa Airlines, Norwegian, Hainan Airlines, Fiji Airways and Royal Air Maroc.

More than 40 countries have also banned the 737 Max from flying in their airspace. China (a huge Boeing customer and a fast-growing commercial aviation market) led the way and was joined by Indonesia, Thailand, Malaysia, Australia, India, Oman, the European Union and Singapore. Canada initially hesitated, but soon reversed course.

Up until March 13, 2019, the FAA also declined to issue a grounding order, saying in a statement tweeted the previous day that there was "no basis to order grounding the aircraft." That was despite a public outcry from a group of senators and two flight attendant unions. But following President Trump's decision to ground the Max that day, the agency cited new evidence it had collected and analyzed. 

Older 737 models, like the 737-700, 737-800 and 737-900, don't use MCAS and aren't affected. 

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Of the four 737 Max versions, only the Max 10 has yet to fly.

Boeing

What was the problem with the warning light?

The Air Current reported March 12, 2019 that the Lion Air plane lacked a warning light designed to alert pilots to the faulty sensor and that Boeing sold the light as part of an optional package of equipment. When asked about the warning light, a Boeing spokesman gave CNET the following statement:

"All Boeing airplanes are certified and delivered to the highest levels of safety consistent with industry standards. Airplanes are delivered with a baseline configuration, which includes a standard set of flight deck displays and alerts, crew procedures and training materials that meet industry safety norms and most customer requirements. Customers may choose additional options, such as alerts and indications, to customize their airplanes to support their individual operations or requirements."

But on April 29, 2019, The Wall Street Journal said that even for airlines that had ordered it, the warning light wasn't operating on some Max planes that had been delivered (a fact the Indonesian accident report confirmed). Then on June 7, 2019, Reps. Peter DeFazio, a Democrat from Oregon, and Rick Larsen, a Democrat from Washington, said they'd obtained information suggesting that even though the plane maker knew the safety alert wasn't working, it decided to wait until 2020 to implement a fix. 

Boeing responded to DeFazio and Larsen in a statement sent to CNET the same day.

"The absence of the AOA Disagree alert did not adversely impact airplane safety or operation," the statement read. "Based on the safety review, the update was scheduled for the MAX 10 rollout in 2020. We fell short in the implementation of the AoA Disagree alert and are taking steps to address these issues so they do not occur again."

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The original version of the 737 first flew in 1967.

Boeing

What kind of MCAS training did 737 Max pilots receive?

Not much, which was a factor cited in both crash reports. As the Indonesian report said, "The absence of guidance on MCAS or more detailed use of trim in the flight manuals and in flight crew training, made it more difficult for flight crews to properly respond."

Though MCAS was new to the Max, existing 737 pilots didn't have to train on a simulator before they could start flying the Max. Instead, they learned about the differences it brought through an hour's worth of iPad-based training. MCAS received scant mention. The reason? It was because Boeing, backed by the FAA, wanted to minimize the cost and time of certifying pilots who'd already been trained on other 737 versions. To do so, Boeing and the FAA treated the Max as just another 737 version, rather than a completely new airplane (which it pretty much is). 

Pilot complaints about the lack of training emerged quickly after the Lion Air crash. On Nov. 12, 2018, The Seattle Times reported that Max pilots from Southwest Airlines were "kept in the dark" about MCAS. The Dallas Morning News found similar complaints from American Airlines pilots four months later.

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The previous model, the 737-900ER, doesn't have the MCAS flight control system.

Boeing/Ed Turner

Are there any other issues with the aircraft besides MCAS?

There are a few.

Have any other reports been issued?

On Oct. 11, 2019, an international flight safety panel issued a Joint Authorities Technical Review that faulted both the FAA and Boeing on several fronts. For the FAA, it said the agency needs to modernize its aircraft certification process to account for increasingly complex automated systems.

For Boeing's part, the report cited the company's "inadequate communications" to the FAA about MCAS, pilot training and shortage of technical staff. The review was conducted by representatives from NASA, the FAA and civil aviation authorities from Australia, Canada, China, Europe, Singapore, Japan, Brazil, Indonesia and the United Arab Emirates.

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How has Boeing responded?

Boeing was fully involved with both investigations early on. On Nov. 6, 2018, just eight days after the first crash, the company issued a safety warning advising 737 Max operators to deactivate MCAS if a flight crew encountered conditions like the Lion Air pilots experienced. It also expressed sympathy for victims' families and pledged $100 million in support, and it quickly backed the US grounding order. 

"There is no greater priority for our company and our industry," Boeing said in a March 13, 2019 statement. "We are doing everything we can to understand the cause of the accidents in partnership with the investigators, deploy safety enhancements and help ensure this does not happen again."

As is common after a crash, Boeing didn't comment on preliminary findings of either investigation, but the day after the Ethiopian crash the company said it would issue a software update that would include changes to MCAS, pilot displays, operation manuals and crew training.

Following the Lion Air accident report, then CEO Dennis Muilenburg said the company was "addressing" its safety recommendations. "We commend Indonesia's KNKT for its extensive efforts to determine the facts of this accident, the contributing factors to its cause and recommendations aimed toward our common goal that this never happens again," he said.

The grounding order also caused Boeing to halt production of the Max for four months in January, 2020. 

Did Boeing know about Max problems before the crashes?

There is evidence that it did. On Oct. 17, 2019, Boeing revealed it revealed text messages between two of the company's top pilots sent in 2016, which indicated the company knew about problems with the MCAS system early on. In one of the messages, a former chief technical pilot for the Boeing 737 described the MCAS' habit of engaging itself as "egregious." 

Later that month, as he appeared before two congressional committees, Muilenburg admitted Boeing knew of the test pilot concerns in early 2019. "I was involved in the document collection process, but I relied on my team to get the documents to the appropriate authorities," he said. "I didn't get the details of the conversation until recently."

Then on Jan. 10, 2020 Boeing released a series of explosive emails and instant messages to Congress in which Boeing employees discussed the 737 Max. Though some expressed regret for the company's actions in getting the aircraft certified -- "I still haven't been forgiven by God for the covering up I did last year," one employee wrote in 2018 -- others openly discussed the 737 Max's flaws and joked about the FAA's approval process. "This airplane is designed by clowns who in turn are supervised by monkeys," another employee wrote. (The New York Times has compiled the documents online.)

Did Boeing change its leadership?

Yes, but it didn't happen quickly. Though Muilenburg apologized to the victims' families in an interview with CBS News in May, 2019, he came under sharp criticism for his response to the crashes. On Oct. 11, 2019, Boeing announced it had taken away his role as chair so that as CEO, Muilenburg could "focus full time on running the company as it works to return the 737 Max safely to service." 

Muilenburg spent the next two months resisting calls for his resignation from his other position, but on Dec. 23, 2019 the company announced that he had stepped down. "The Board of Directors decided a change in leadership was necessary to restore confidence in the company moving forward as it works to repair relationships with regulators, customers, and all other stakeholders," Boeing said in a statement. Chairman David Calhoun officially replaced Muilenburg on Jan. 13, 2020. 

Calhoun had defended Muilenburg before taking the top role, but in a March 5, 2020 interview with the New York Times he said his predecessor had needlessly rushed production of the Max before the company was ready. "I'll never be able to judge what motivated Dennis, whether it was a stock price that was going to continue to go up and up, or whether it was just beating the other guy to the next rate increase."

Separately, on Oct. 22, 2019, the company said it replaced Boeing Commercial Airplanes CEO Kevin McAllister, the official overseeing the 737 Max investigation, with Stan Deal, former president and CEO of Boeing Global Services.

What has the FAA's role been?

Complicated. The agency quickly came under fire on multiple fronts over the crashes. Congress, the FBI, the Justice Department's criminal division and Secretary of Transportation Elaine Chao all called for investigations of the FAA's certification process. Under an FAA program, Boeing was allowed to participate in the process, meaning that it inspected its own plane.

But on Jan. 16, 2020, an independent panel set up by the Department of Transportation (the FAA is a division of the DOT) dismissed that criticism. In its report, the committee found no significant problems with how the Max was cleared to fly. Though the committee said the FAA could improve the certification process, it saw no need for substantial changes (see next question). 

Outside of the certification process, the FAA has slapped Boeing with two fines for installing substandard or unapproved equipment in some Max planes. With the first fine, which the FAA proposed in January 2020 for $5.4 million, the agency said Boeing used improper equipment to guide the slats on 178 Max planes. Positioned at the leading edge of each wing, slats are deployed at take-off and landing to provide more lift. The FAA also accused Boeing of installing a guidance system on 173 Max planes that used sensors that hadn't been properly tested. The proposed penalty is $19.68 million.

And that's not all. According to The Wall Street Journal, both the FAA and the Justice Department are investigating whether Boeing workers mistakenly left debris in fuel tanks or other interior spaces of completed aircraft.

Has Congress gotten involved?

Yes. In March 2020, the House Committee on Transportation and Infrastructure released a report on the design, development and certification of the 737 Max and the FAA's oversight of Boeing. It said "acts, omissions, and errors occurred across multiple stages and areas of the development and certification of the 737 MAX." The report went on to identify five specific issues.

  • Production pressures: There was tremendous financial pressure on Boeing and the 737 Max program to compete with the A320neo, leading the company to rush the plane into service. 
  • Faulty assumptions: Boeing made fundamentally faulty assumptions about critical technologies on the 737 Max, most notably with MCAS.
  • Culture of concealment: In several critical instances, Boeing withheld crucial information from the FAA, its customers and 737 Max pilots.
  • Conflicted representation: The FAA's current oversight structure over Boeing creates inherent conflicts of interest that have jeopardized the safety of the flying public. 
  • Boeing's influence over the FAA's oversight: Multiple career FAA officials documented examples of FAA management overruling the determination of the agency's own technical experts at the behest of Boeing.

On Sept. 16, the House Transportation Committee issued a report that blamed the crashes on a "horrific culmination" of failures at Boeing and the FAA. "In several critical instances, Boeing withheld crucial information from the FAA, its customers, and 737 MAX pilots," the report said. And as for the FAA, "the fact that a compliant airplane suffered from two deadly crashes in less than five months is clear evidence that the current regulatory system is fundamentally flawed and needs to be repaired."

Then on Dec. 21 after a Senate report faulted Boeing's and the FAA's initial review of the Max, Congress passed legislation that reforms the FAA's protocols for certifying new aircraft. Among other things the bill eliminates some parts of the process that allows manufacturers to certify their own planes and creates new safety review procedures and whistleblower protections.

What happened during the grounding period?

First off, Max airlines had to look for parking spaces for the roughly 300 Max aircraft Boeing had delivered by the time the worldwide order went into effect. That's a tremendously complicated effort by itself.

But while airlines can't fly the plane (except to ferry empty aircraft from one airport to another) Boeing was able to conduct test flights for evaluating its proposed fixes

On May 16, 2019, the company said its updates were largely complete after more than 135 test flights. Five months later, on Oct. 22, the company said it had made "significant progress" toward that goal by adding flight control computer redundancy to MCAS and three additional layers of protection. It also had conducted simulator tests for 445 participants from more than 140 customers and regulators. Boeing provided a further progress report Nov. 11. 

Boeing and the FAA finally began the recertification flights on June 29. The flights attempted to trigger the steps that led to the two crashes and confirm that MCAS isn't activating erroneously. The FAA also reviewed pilot training materials and FAA Administrator Steve Dickson piloted the plane on a Sept. 30 test flight to evaluate Boeing's changes. Speaking to reporters after the flight he said he "liked what I saw."

When did the FAA lift the grounding order and what are its proposed fixes?

The agency lifted the order on Nov. 19. The mandatory fixes include:

  • Avoid relying on a single angle-of-attack sensor that's giving faulty readings, MCAS must compare data from more than one sensor.
  • All aircraft must have a warning light that shows when two sensors are disagreeing.
  • MCAS will activate only once rather than activating repeatedly, another factor that contributed to both crashes.
  • If MCAS is erroneously activated, flight crews will always be able to counter the movement by pulling back on the control column. 
  • Pilots will need more rigorous training on MCAS including time in a Max simulator (see next question). 
  • Outside of MCAS, the FAA also identified other modifications Boeing must make, including separating two bundles of wiring that power control surfaces on the aircraft's horizontal stabilizer to ensure redundancy if one of the bundles fails. 

How will pilot training change?

Simulator time focusing on MCAS will now be required, a change from a position the FAA previously took. It took lobbying from pilots and regulatory officials from other countries, like Canadian Transport Minister Marc Garneau, to change that decision.

They won an influential supporter on June 19, 2019, when "Miracle on the Hudson" Capt. Chesley B. "Sully" Sullenberger argued before a congressional committee that simulator training should be required before pilots take the Max back into the air. He also said the original design of MCAS was "fatally flawed and should never have been approved."

On Jan. 7, 2020, Boeing agreed when it issued a recommendation that pilots receive simulator training on MCAS before the Max returns to service. Simulator sessions will require extra time and expense for airlines struggling to get their Max fleets back in the air.

What happens next?

Before airlines can fly the Max again, Boeing must work with the airlines to make the required fixes and retrain pilots. Only then will the FAA sign off on certification for each aircraft. That will take time. 

Three US airlines currently have the aircraft in their fleets: Southwest, American and United. American resumed flights Dec. 29 with a Max flight between Miami and New York LaGuardia. The airline says it will continues to add Max flights, "with up to 36 departures from our Miami hub depending on the day of the week." United predicts a return by the first quarter of next year while Southwest says it won't start flying the Max until at least the second quarter.

But that's just in the US. Aviation regulatory agencies around the world also need to approve the fix before they'll let the Max fly to the countries they oversee. Traditionally, they've followed the FAA's lead on such matters, but Transport Canada, China, the European Aviation Safety Agency and other countries have conducted independent tests of the plane while working with the FAA. They're working on different timelines -- though the EU should finish by the end of the year -- and they may ask for more changes. Brazil's National Civil Aviation Agency lifted its grounding order Nov. 25 and commercial flights have resumed.

Boeing and airlines also will need to ferry the hundreds of Max aircraft stored around the world to airports where passenger flights can begin.

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A Boeing 737 Max 7 lands at Boeing Field in Seattle after a test flight to evaluate the MCAS software fix.

Paul Christian Gordon/Boeing

How will I know I'm booked on a Max flight and will I be able to change my reservation?

Your aircraft type will be listed in the flight details as you book. Some airlines will spell out the full aircraft name as "737 Max," while other carriers may shorten it to "7M8." If you're not sure, contact a reservations agent to confirm. Just remember, though, that airlines can change the aircraft type for your flight at the last minute.

For now at least, all US airlines operating the Max will allow you to change your flight with penalty or cancel your trip for either a full refund or a travel credit. The exact details will vary, and I wouldn't expect the policies to last forever, so click the link above and confirm with your airlines as you book.

How important is the Max series to Boeing?

Hugely important. The battle for the 150- to 200-seat aircraft market between Boeing and Airbus is fierce, and Airbus is currently winning the battle for orders. As of Oct. 31, 2020, Boeing had 4,102 737 Max orders on the books from from both existing operators and airlines like Alaska and Ryanair. Ryanair ordered an additional 75 aircraft on Dec. 3.

Following the second crash, though, new orders slowed dramatically and some carriers canceled or delayed their orders, a trend only hastened by the travel slowdown from the coronavirus pandemic. But Boeing did get occasional occasional bits of good news. On June 18, 2019, at the Paris Air Show, International Airlines Group said it would consider buying 200 737 Max 8s and 10s. Four months later at the Dubai Air Show, Boeing reported 737 Max orders from Air Astana and SunExpress

In any case, though, Boeing will will have its work cut out for it in assuring both airlines and the flying public that the Max is safe.

Has a commercial aircraft been grounded before?

Yes. In the most recent example, the FAA grounded the Boeing 787 for three months in 2013 after a series of nonfatal battery fires. Before that, the FAA grounded the Douglas DC-10 for a month in 1979 after a crash near Chicago O'Hare Airport killed 271 people on board, plus two on the ground. (Outside of the Sept. 11, 2001, terrorist attacks, that remains the deadliest airplane crash on US soil.) The Chicago crash was ultimately attributed to improper maintenance. The crash of a DC-10 in 1974 in France, killing 346 people, was caused by a design flaw on a cargo hold door latch.

Outside the US, both Qantas and Singapore Airlines voluntarily grounded their Airbus A380s for a couple of days after a Qantas flight from Singapore to Sydney in 2010 had an uncontained engine failure

Are airplanes now too complicated?

On March 12, 2019, Trump tweeted that airplanes are "becoming far too complex to fly." The reality isn't quite that simple. Commercial airliners have used automated systems for decades (that's what an automatic pilot is). The Lockheed L-1011, introduced in 1972, could land itself. Most airliners flying today also are "fly by wire," meaning that a pilot's commands are carried as electronic signals (rather than over hydraulic lines) to an aircraft's control services. Flight computers also continually stabilize an aircraft during flight without input from the flight crew. Boeing and Airbus have different philosophies for this interaction, but explaining those could take a book.

So the basic concept of MCAS is nothing new. But crews need to be properly trained to use automated systems, recognize when they may be at fault and override them if necessary. As the accident reports have indicated, a lack of training about MCAS contributed to the Max 8 crashes. Airline pilots are thoroughly trained to fly an aircraft under extraordinary circumstances, but they need accurate information about factors like airspeed and altitude to be able to make quick decisions in an emergency.

Correction, Jan. 10, 1:54 p.m. PT: This story initially misstated the status of Malaysia's Malindo Air at the time of the first crash.