The Federal Aviation Administration on Wednesday cleared the way for Boeing’s 737 Max to resume flying, 20 months after it was grounded following two fatal crashes blamed on faulty software and a host of company and government failures.

The decision ends a devastating saga for Boeing, which had predicted billions of dollars in losses stemming from the Max crisis even before the coronavirus pandemic dealt a ruinous blow to global aviation. The agency’s chief, Stephen Dickson, signed an order Wednesday formally lifting the grounding.

“The path that led us to this point was long and gruelling, but we said from the start that we would take the time necessary to get this right,” he said in a video message. “I am 100 per cent comfortable with my family flying on it.”

The Max was grounded worldwide in March 2019 when the FAA joined regulators in dozens of other countries in banning the plane after the crashes in Indonesia and Ethiopia killed all 346 people on board.

Investigators have attributed the crashes to a range of problems, including engineering flaws, mismanagement and a lack of federal oversight. At the root was software known as MCAS, which was designed to automatically push the plane’s nose down in certain situations and has been blamed for both crashes.

In August, the FAA determined that a series of proposals by Boeing — including changes to MCAS, flight crew training and the jet’s design — “effectively mitigate” its safety concerns. Dickson, a former Delta Air Lines pilot, took the controls on a test flight in September, saying he liked what he saw.

In a news conference on Tuesday in anticipation of the FAA announcement, relatives of victims on the second plane that crashed, Ethiopian Airlines Flight 302, questioned whether Boeing had done enough to address safety concerns with the plane.

“Aviation should not be a trial-and-error process; it should be about safety,” said Naoise Ryan, whose husband, Mick, was aboard that flight on March 10, 2019. “If safety is not prioritised, then these companies should not be in business.”

In a letter to employees, Boeing’s chief executive, David Calhoun, welcomed the lifting of the ban, promising to proceed deliberately with the plane’s return to service and to “never forget” the victims of the crashes.

“We will honour them by holding close the hard lessons learned from this chapter in our history to ensure accidents like these never happen again,” he said.

Now that the FAA has lifted its grounding order, regulators around the world are expected to follow suit, though some may take their time in wrapping up their own in-depth reviews.

The agency has worked with its counterparts in Canada, the EU and Brazil on revised pilot training requirements for the Max.

Even in the US, it could be months before the Max starts carrying passengers again. The FAA must still approve pilot training procedures for each US airline operating the Max, planes need to be updated, and airlines suffering from a huge decline in traffic during the pandemic may feel little urgency to act quickly.

On an investor call last month, the American Airlines chief executive, Doug Parker, predicted that the carrier would not resume Max flights before late December if the order came in November. Southwest Airlines and United Airlines have said they probably will not fly the plane until next year.

“United’s Max fleet won’t return to service until we have completed more than 1,000 hours of work on every aircraft, including FAA-mandated changes to the flight software, additional pilot training, multiple test flights and meticulous technical analysis to ensure the planes are ready to fly,” the airline said in a statement, adding that it expects to start flying the plane in the first quarter of next year.

The Air Line Pilots Association, which represents nearly 60,000 pilots in North America, including those at United and Delta, said in a statement that it is still reviewing changes to training procedures, but said that the proposed engineering fixes “are sound and will be an effective component that leads to the safe return to service of the 737 MAX.”

Nonetheless, the FAA decision removes some uncertainty as Boeing seeks to rehabilitate its reputation, start fulfiling longstanding orders for the Max and gauge how soon and how fully air travel will recover.

The company has lost more than 1,000 orders this year, mostly for the Max, after accounting for orders that either were cancelled or are likely to fall through.

Aircraft contracts typically allow buyers to cancel or renegotiate terms if deliveries are delayed, adding to the urgency for Boeing to resume delivering the planes. Still, the company has more than 4,200 orders in its backlog, most of them for the Max.

New York Times News Service