More than a dozen airlines along with the governments of China and Indonesia grounded a new version of Boeing’s most popular jet on Monday, as the American aerospace giant scrambled to deal with the fallout from a deadly plane crash in Ethiopia.
It was the second time in a matter of months that this model, the 737 Max 8, crashed just minutes after an erratic takeoff, leaving Boeing and safety regulators around the globe racing to determine what went wrong and whether the plane is safe to fly.
Investigators in Ethiopia on Monday said the flight data recorder and the cockpit voice recorder had both been recovered, which could speed up the investigation. But it could still take time to discern whether the cause of the crash of Ethiopian Airlines Flight 302, which killed 157 people, was a faulty plane, pilot error or something else entirely.
In October, a Lion Air flight crashed under similar circumstances in Indonesia, killing all 189 people on board. While the cause of that crash is still under investigation, Indonesian and American aviation authorities have raised the possibility that software in the Max 8 was partly to blame.
Those similarities immediately provoked concern among carriers, pilots, flight attendants, passengers and investors. At least 20 airlines around the world have grounded their 737 Max 8 planes, largely in China and Indonesia. In all, about 130 of the roughly 350 new jets that were in service have been pulled from use.
The Federal Aviation Administration said on Monday that it would examine the data and act as necessary. “External reports are drawing similarities between this accident and the Lion Air Flight 610 accident,” the American regulator said in a statement. “However, this investigation has just begun and to date we have not been provided data to draw any conclusions or take any actions.”
Southwest Airlines and American Airlines, the only two carriers in the United States that use the jet, both said they would continue to fly the plane. At least 16 more carriers around the world are still flying the jet.
Boeing’s chief executive, Dennis Muilenburg, expressed sympathy for the victims and their families on Monday, saying the company was working closely with American and Ethiopian authorities to investigate the accident. He said Boeing was committed to ensuring the safety and quality of its planes. But he cautioned against speculating about “the cause of the accident without all the necessary facts,” adding that it could “compromise the integrity of the investigation.”
The uncertainty over the cause of the latest crash has put Boeing on the defensive. The 737 Max is the company’s best-selling jet ever, and it is expected to be a major driver of profits in the future. Around 5,000 of the planes are on order, with a list price of $120 million for the Max 8 version.
Shares of the company fell 5 percent on Monday, as pressure mounted from various corners.
The Association of Flight Attendants sent a letter to the F.A.A. on Monday calling for a review of the 737 Max. “We need help from the regulators when the entire world is looking at two catastrophic incidents that happened on the same aircraft type within five months of each other,” said Sara Nelson, the president of the flight attendants’ union. “Our system is so safe that these things don’t happen today. That is why people are questioning what is going on here.”
Pilots also raised questions about the safety of the plane. “We’re very concerned about why two brand-new aircraft suddenly pitched over and nosed into the ground,” said Rory Kay, a former top safety official at the world’s largest pilot union and a senior pilot and pilot trainer at a major United States airline. “This is not the dawn of aviation. We’ve evolved, planes have evolved.”
Dennis Tajer, a spokesman for the American Airlines pilot union and a 737 pilot, said that the Lion Air crash hurt the reputation of the 737 Max in the eyes of some of his members and that the Ethiopian accident had prompted new questions from them. “I think there needs to be further review into the certification process” for the aircraft, Mr. Tajer said. “Everybody should be looking at this.”
In Washington, two senators, Dianne Feinstein of California and Richard Blumenthal of Connecticut, went a step further, calling on the F.A.A. to ground all Boeing 737 Max 8s until the investigation into the Ethiopia crash was complete.
Some passengers tried to rebook their flights to avoid a 737 Max 8. Carriers that hadn’t grounded the plane sought to reassure customers, providing information about the jet’s safety.
Alicia Winnett and her husband had planned to fly Air Canada from Vancouver to Calgary on Friday. Ms. Winnett contacted the carrier hoping to switch to a later flight on an Airbus 320, but Air Canada told her that was not possible.
“I just cannot sit on a Boeing 737 Max 8 with confidence,” she said.
Chinese airlines operated other aircraft as substitutes for the 737 Max 8s on 256 flights in the first several hours after the grounding of the jets, according to VariFlight, an online flight-tracking service based in China. Twenty-nine flights were canceled.
A key question for investigators is whether the same system suspected to have played a role in the Lion Air crash contributed to the Ethiopia disaster. Indonesian and American aviation authorities have raised the possibility that a new system in the 737 Max jets — and the pilots’ lack of familiarity with it — could have contributed to the crash of Flight 610. The so-called maneuvering characteristics augmentation system, known as MCAS, was a new software system that could automatically change the plane’s trajectory.
Boeing and regulatory agencies have since informed pilots and airlines of the new system. It was not immediately known if pilots for Ethiopian Airlines, which has a strong safety reputation, were given additional training.
After the Lion Air crash, Boeing was expected to update the software. On Monday night, Boeing said it was working with the F.A.A. on an upgrade to “be deployed across the 737 MAX fleet in the coming weeks.”
Details from Ethiopia were still scant. The pilot of the flight on Sunday sent out a distress call shortly after takeoff, and was cleared to return to the airport. Before it could do so, witnesses described an aircraft that swerved and dipped wildly in its final moments, spewing smoke and making unusual noises before it hurtled into the ground.
One man told Ethiopia’s national broadcaster that the jet appeared to briefly gain altitude shortly before it smashed into a field.
Another witness, who identified himself by only one name, Feyissa, said he had seen the aircraft circling four or five times. “Then the plane came down almost vertically at great speed, hard and loud — fire, smoke and everything happened so fast,” he said.
Aviation experts have cautioned that while witness accounts can help in an investigation, they are not necessarily accurate and are of limited value in helping pinpoint the cause or causes of a crash.
The victims were from more than 35 countries and included at least 22 employees of United Nations-affiliated agencies.
Persistent concerns about the Boeing 737 Max 8 could have an outsize influence on global travel. Airlines often fly those jets, and their earlier versions, multiple times a day.
“Because it’s the most widely used jetliner, when there are unanswered questions about it and groundings, it can have a huge ripple effect in the confidence of the aviation system,” said Bill Adair, author of “The Mystery of Flight 427,” a book about a 737 crash in 1994. “But it’s important not to jump to conclusions, and it’s awfully early to be grounding airplanes.”
Boeing has faced periods of scrutiny in the past. A series of 737 crashes in the 1980s and 1990s prompted concerns about the plane’s safety, though Boeing kept producing and selling them.
In the last decade, Boeing faced a crisis when lithium-ion batteries in the 787 Dreamliner were catching fire. To address that problem, Boeing assembled a team of experts from around the company, many of whom hadn’t initially worked on the 787.
“It was a total mobilization, they had hundreds of people working on it,” said John Hall, a former Boeing engineer who was part of the effort. “This is a far more difficult call. It’s not clear that there’s anything wrong with the airplane. They’ve had two crashes now, but they don’t know the cause.”
On Sunday, Boeing dispatched a so-called technical assistance team — a group of several engineers and experts based in the United States — to assist with the investigation in Ethiopia.
The company communicated with the 59 carriers that use the 737 Max 8 and 9 models, and Mr. Muilenburg, the Boeing chief, kept his board updated on developments.
Late Monday, Mr. Muilenburg sent an email to employees with an update on the situation.
“I know this tragedy is especially challenging coming only months after the loss of Lion Air Flight 610,” he wrote, according to a copy of the email reviewed by The New York Times. “While difficult, I encourage everyone to stay focused on the important work we do.”