The US Federal Aviation Administration on Wednesday cleared Boeing's 737 MAX for flight after nearly two years and two crashes that killed 346 people.
Before the plane that was grounded around the world in March 2019 returns to the sky, the FAA must approve pilot training procedures for each US airline operating it; planes need to be updated with critical software; and computers mandated by the FAA.
The MAX was grounded around the world after an Ethiopian Airlines jet crashed six minutes into flight from Addis Ababa. That happened less than five months after another MAX flown by Indonesia's Lion Air plunged into the Java Sea.
It was discovered that a safety feature meant to stop the plane from climbing too fast and stalling had improperly forced the nose of the plane down despite the pilots' attempts to right it, causing the crashes.
When the MAX, the best-selling plane in Boeing's fleet, does return to service it will be facing air travel decimated by the COVID-19 pandemic.
The first to fly will be American Airlines, which has scheduled a MAX round-trip flight from Miami to New York's La Guardia Airport for Dec 29. United Airlines expects to schedule flights on the MAX in late January or February.
To provide reassurance, American plans for corporate customers to tour the plane and hear from experts. The airline says passengers will be able to see if they are booked on a 737 MAX and will be able to change to another flight if they wish.
FAA chief Stephen Dickson, who signed an order Wednesday rescinding the grounding, said on CNBC Wednesday that the design and pilot-training changes required by the FAA make it "impossible for the airplanes to have the same kind of accident that unfortunately killed 346 people".
In an FAA video message, Dickson said that for the time being, the FAA will inspect every new MAX before letting the planes fly.
United Airlines said Wednesday that it expected to start flying the MAX in the first quarter of next year. Southwest Airlines said it didn't expect to resume flights until the second quarter.
The Air Line Pilots Association, which represents nearly 60,000 pilots in North America, said in a statement that it was still reviewing changes to training procedures, but that the proposed engineering fixes "are sound and will be an effective component that leads to the safe return to service".
The plane' flight computer — called the Maneuvering Characteristics Augmentation System, or MCAS — proved to have serious flaws. In both crashes, pilots struggled to keep their aircraft aloft as MCAS repeatedly pushed the nose down. They were unable to disengage the system, which eventually sent them into dives from which they could not recover.
Boeing modified the MCAS software and added other safety features to make sure that pilots can immediately disengage the system.
On Tuesday, the House passed a bipartisan bill aimed at changing FAA certification procedures and requiring an expert panel to review Boeing's safety culture.
The move follows multiple congressional hearings on the crashes that led to criticism of the FAA for lax oversight and of Boeing, which was accused of rushing to implement a new software system that put profits over safety and ultimately led to the firing of its CEO.
One critic of the changes made to the MAX who says they aren't enough is consumer advocate Ralph Nader, whose 24-year-old niece died in the Ethiopian Airlines crash.
On a conference call with reporters on Tuesday, family members of the Ethiopian Airlines crash victims expressed exasperation about how a new jetliner from a highly regarded aircraft maker like Boeing could fall from the sky — not just once, but twice.
"It doesn't seem real. How could this happen?" asked Naoise Ryan, whose husband Michael Ryan died in the crash along with six colleagues from the United Nations World Food Program. "Not a single person has been held to account" and "aviation should not be a trial-and-error process."
The process of approving the plane has cost Boeing more than $20 billion, according to the company..