US safety regulators have cleared Boeing’s 737 Max plane to fly again, lifting grounding orders put in place in March 2019 after two deadly crashes.
The move marks a key milestone for the firm, which was thrust into crisis by the tragedies and investigations that blamed it for the accidents.
Its financial woes deepened this year as air travel slowed due to the virus.
Existing aircraft will need to be modified before going back into service, with changes to their design.
Safety regulator, the US Federal Aviation Administration (FAA), said the clearance would not allow the plane to “return immediately” to the skies.
Alongside the software and wiring changes, pilots will also need training.
The FAA said the design changes it had required “have eliminated what caused these particular accidents”.
The boss of the FAA, said he was “100% confident” in the safety of the plane.
“We’ve done everything humanly possible to make sure” these types of crashes do not happen again,” Steve Dickson said.
The approval comes roughly a year after Boeing had first hoped but too soon for many of the victims’ families.
The US is the first to reverse the grounding orders, which hit the firm around the world in March 2019. European aviation officials have said they are close to making a similar decision.
The crashes in Indonesia and Ethiopia came within five months of each other and together killed 346 people. They have been attributed to flaws in automated flight software called MCAS, which prompted the planes to nosedive shortly after take-off.
A US congressional report last month said Boeing’s rush to production, a decision to ignore internal safety concerns and concealment of key changes to the plane, including pilot training needs, contributed to the accidents.
It also faulted the FAA for oversight lapses, including “excessive delegation to Boeing”.
Boeing has estimated the cost of the grounding at roughly $20bn.
Before the crashes, Boeing churned out more than 50 of the popular 737 Max per month. But airlines around the world have cancelled and delayed orders due in part to the pandemic.
Last month, Boeing said it did not expect its production rate to top 30 planes a month until 2022. It warned investors of a backlog of about 450 737 Max planes, of which only about half of which would be delivered by the end of next year.