The Federal Aviation Administration lifted its ban on the Boeing 737 Max on Wednesday, 20 months after the aircraft was grounded following two crashes within five months that killed 346 people. The action means the FAA is satisfied that software and other fixes, and new pilot training, make the plane safe to fly again.

The FAA said it brought unparalleled scrutiny to the Max this time. Boeing and federal regulators were faulted in several investigations of the crashes for missing fatal flaws in the aircraft. Investigators pointed to lax government oversight and problems during the certification process.

The Max was grounded worldwide on March 13, 2019, after the FAA said satellite data showed “the possibility of a shared cause” for two crashes, one on Oct. 29, 2018, in Indonesia and the other on March 10, 2019, in Ethiopia. Investigators later found that problems with an automated flight control feature led to both crashes.

Administrator Steve Dickson of the FAA signed Wednesday’s order ending the ban, and the agency said it can “assure the global community that the 737 MAX is safe to operate.”

“We have not left anything to chance here,” Dickson added. “I would put my own family on it, and we will fly on it.”

Boeing said the company had undertaken a “thorough assessment to ensure that our systems meet all regulatory standards, reflect industry best practices and also incorporate learnings from independent reviews.”

The ban is being lifted in a significantly changed environment, with the airline industry decimated by the coronavirus pandemic. Passenger numbers remain far below normal levels, tens of thousand of airline workers have been laid off, and carriers are losing billions of dollars.

Even with the FAA action, it will still be several weeks before the first Max jets return to the skies. Hundreds of the aircraft were grounded worldwide, including more than 70 in the United States, and others were built by Boeing and have yet to be delivered to customers. The planes, which have been parked for extended periods, must be inspected and updated, and more than 14,000 pilots need to be retrained at U.S. carriers alone.

Although some airlines are ready to fly the Max again — the more fuel-efficient planes will save them money — it is unclear whether the public will be eager to return, once travel rebounds from the pandemic, perhaps after widespread immunization with promising vaccines next year.

Tarnished reputation

The U.S. government had been viewed by many as the global standard-bearer for aviation safety. But the FAA’s certification that the Max was safe in 2017, and its initial reluctance to ground the aircraft after the Ethiopia crash, tarnished the agency’s credibility. Aviation safety authorities in China, the European Union and many other countries were quicker to act.

Revelations that some Boeing employees raised concerns internally about some of the problems cited in the crashes, sent mocking and manipulative messages about regulators, and led a campaign to prevent the FAA from requiring costly simulator training for Max pilots underscored flaws in the regulatory process, which allows the agency to delegate much of the detailed work of certification to the manufacturer.

Families of those killed in the crashes remain unconvinced of the plane’s safety, and they appealed to the FAA to release more technical details about Boeing’s fixes so independent experts can assess whether they are sufficient to ensure that the Max is safe.

“Prove that safety is your priority,” said Naoise Ryan, who lives in Ireland and described the effect the death of her husband, Mick Ryan, in the Ethiopian Airlines crash had on their young daughter, Saorlaith.

The girl had begged her father not to leave on the work trip for the U.N. World Food Program. But her parents knew he wasn’t taking on a dangerous assignment, so, Ryan said, “there was nothing to be concerned about.”

Ryan said her daughter has night terrors, and after a birthday wish that her father return went unfulfilled, the child gave up on wishing.

The couple’s son, Macdara, was just a few months old at the time of the crash and will never know his father.

“Our family is broken,” Ryan said.

Michael Stumo, whose daughter Samya died in the Ethiopia crash, said short of much more comprehensive technical disclosures by the FAA and agency requirements for additional safety measures, the Max cannot be trusted.

“This plane should be avoided by the flying public,” he said.

Crash investigators said an automated feature on the Max known as the Maneuvering Characteristics Augmentation System (MCAS) repeatedly forced the noses of the planes down, overwhelming pilots and leading to the crashes.

The FAA order on Wednesday requires the overhaul of MCAS developed by Boeing, as well as other improvements to the flight control system. The updated software makes MCAS less powerful, so a pilot can more easily regain control of the plane, Boeing said. The plane also now compares input from two external sensors rather than one. Investigators determined that faulty data being fed to a sole sensor caused MCAS to repeatedly engage before the crashes.

The FAA required that a cockpit alert — meant to flag problems with the sensors, but that didn’t work unless airlines chose that option — is on all planes. The agency is also ordering the rerouting of wiring to prevent a potential “short circuit” in a horizontal stabilizer critical for safe flight.

“We will never forget the lives lost in the two tragic accidents,” said David Calhoun, Boeing’s chief executive. “These events and the lessons we have learned as a result have reshaped our company and further focused our attention on our core values of safety, quality and integrity.”

The FAA’s decision to unground the Max comes as attention has largely shifted away from the Max’s troubles and to the industry's struggles to survive an economic crisis analysts said is worse than that after the terrorist attacks of Sept. 11, 2001.

“The pandemic has completely obscured so much of the news and drama around the Max that was being discussed last year,” said Henry Harteveldt, president of Atmosphere Research Group, a San Francisco-based aviation industry research company.

The timing of the ungrounding may work in airlines’ favor, he said. Passenger volumes remain a fraction of what they were a year ago, and some experts say they don’t expect a significant rebound for several years.

“What will ultimately make the plane acceptable is when it does its job — when it operates without incident,” Harteveldt said. “You know that if a coffee maker breaks [on the plane] it’s going to be news, but at this point I’m hopeful it will have a smooth return to service. The traveling public should have much more confidence in the plane.”

American Airlines said it expects to resume service with the Max at the end of the year, starting with one daily round-trip flight between Miami International and New York’s LaGuardia airports Dec. 29 through Jan. 4, with dozens more departures from Miami being added later.

Southwest Airlines CEO Gary Kelly said he expects it to take three or four months before the planes are ready for passenger service. The airline has 34 of the jets in its fleet, the most of any U.S. carrier.

Kelly is upbeat about bringing back the Max, and said the process for returning it to regular service will be “deliberate and structured.” In addition to necessary changes to the plane’s software, the carrier will have to train its nearly 7,000 pilots — including simulator time.

“It is our most cost-effective aircraft,” Kelly said on a recent earnings call. “It is our most reliable aircraft. It is our most environmentally friendly aircraft, and it’s our most comfortable aircraft. So we really look forward to flying it again.”

United said it expects to resume service with the Max in the first quarter of 2021 but does not yet have an exact date.

Rebuilding trust

U.S. officials and Boeing executives spent more than 18 months working with international aviation authorities to try to rebuild trust.

Boeing presented key software and other changes it said will guarantee the plane’s safety. The FAA took cues from its key foreign counterparts, who were heavily involved in efforts to reexamine the plane’s critical systems and the safety assumptions that went into them.

Some vital international partners, including the E.U. Aviation Safety Agency, have indicated that they also are close to ungrounding the plane, a much-needed outside endorsement for the fixes made by the beleaguered American manufacturer and a key objective of U.S. officials, whose credibility has come under assault.

But the European regulators also are calling for safety measures beyond those the FAA is requiring, including a new “synthetic” sensor on the Max as an extra layer of protection.

The synthetic sensor would augment the two physical “angle of attack” sensors on the plane. Faulty data from one of the sensors, which measure the relative position of the plane’s nose and oncoming wind, fed MCAS with bad information, which investigators said was a key factor in the crashes.

The European agency said that Boeing has agreed to such an addition, and that planes would be retrofitted over time, with added procedures for pilots in the meantime to reduce potential risks.

EASA spokeswoman Janet Northcote said the agency also will prohibit pilots from making certain “precision approaches” at airports “surrounded by difficult terrain.” Those would be in place temporarily, pending additional mitigation from Boeing, she said.

Northcote said the European agency and Canadian authorities also will include an instruction allowing pilots to halt an erroneous stall warning, known as a “stick shaker,” part of the cacophony of alarms that distracted pilots before the two crashes.

Europe’s draft ungrounding order will be published for comment this month and is expected to be finalized around the end of the year or early next year, she said. The publication of that final airworthiness directive “is the moment when EASA sends the message that in its view it is safe to fly on the Max,” Northcote said.

The FAA said its work on the Max was backstopped by an independent team of experts, including from the Air Force and NASA, which reviewed the proposed fixes to make sure they were sufficient.

The Air Line Pilots Association, which represents more than 59,000 pilots at 35 airlines in the U.S. and Canada, said it thinks the engineering fixes to the flight critical aircraft safety systems are sound. While the steps taken to return the plane to service are a “positive step forward,” it added, it is critical that there be “significant” improvements to the FAA’s broader certification process.

Broader issues raised by the Max crashes have yet to be resolved.

In September, congressional investigators pointed to a dangerously cozy relationship between the FAA and Boeing.

The two crashes “were the horrific culmination of a series of faulty technical assumptions by Boeing’s engineers, a lack of transparency on the part of Boeing’s management, and grossly insufficient oversight by the FAA — the pernicious result of regulatory capture on the part of the FAA with respect to its responsibilities to perform robust oversight,” according to the investigation by the House Committee on Transportation and Infrastructure.

FAA leaders have not pushed to overhaul the agency’s system for overseeing Boeing, and congressional action to require improvements has faced delays. But with the Max hours from being ungrounded, the House passed a bill on Tuesday to strengthen the FAA’s oversight of Boeing and other aircraft manufacturers.

The legislation, shaped by the extensive transportation committee investigation, would give the FAA new authority over Boeing engineers specially approved to conduct safety work on behalf of the government. It also would provide the FAA with $30 million in coming years to recruit engineers and other experts to conduct oversight.

“A U.S. commercial airplane manufacturer and, candidly, the Federal Aviation Administration broke the public trust. Three hundred forty-six innocent people died,” said Rep. Peter A. DeFazio (D-Ore.), chairman of the committee and the bill’s leading advocate.

The bipartisan bill also would assemble a panel of experts to review Boeing’s safety culture, extend whistleblower protections to employees at manufacturers and create new guardrails designed to protect the independence of technical experts at the FAA and in industry.

On Wednesday, the Senate Commerce Committee advanced similar legislation. The moves raise the prospect of a package of legal changes being finalized before the end of the congressional term.

Sen. Roger Wicker (R-Miss.), the committee’s chairman, commended the FAA for following a careful process in reviewing the Max and said his committee will continue its oversight. “Restoring public confidence is of paramount importance,” he said in a statement.

The FAA has told lawmakers that it expects to need to expand its safety workforce by at least 236 people, based on recommendations issued by an international panel that examined its role in initially approving the Max as safe.

In a bill introduced last week, the Senate Appropriations Committee said it would authorize the agency to hire 75 of them in the coming year, and would provide an extra $5 million so the FAA could accelerate its hiring, which the panel deemed “insufficient” to address the challenges.