The Boeing 737 Max has been cleared to fly again by the US Federal Aviation Administration two years after it was grounded following two fatal crashes.
Announcing the decision on Wednesday, America’s air safety agency said it undertook a comprehensive and methodical 20-month review process in the wake of two 737 Max crashes, within five months of each other, that killed 346 passengers and crew members.
The 737 Max was grounded by airlines in March 2019 after the crash of an Ethiopian Airlines jet, which happened less than five months after another Max flown by Indonesia’s Lion Air plunged into the Java Sea.
Boeing was heavily criticised for rushing to implement a new software system that put profits over safety and ultimately led to the dismissal of its chief executive.
The planes will not return to the skies immediately as the Federal Aviation Administration (FAA) says it must approve pilot training changes for each US airline and airlines must perform required maintenance on the planes.
Nearly 400 Max jets were in service worldwide when they were grounded, and Boeing has built and stored about 450 more since then. All these aircrafts must now undergo maintenance and be modified before they can fly.
It was estimated that 15 more crashes involving a 737 Max could have happened without the faults being fixed.
Sales of new planes have plunged because of the Max crisis and the coronavirus pandemic; Boeing says orders for more than 1,000 Max jets have been cancelled or removed from Boeing’s backlog this year.
“Those regulators have indicated that Boeing’s design changes, together with the changes to crew procedures and training enhancements, will give them the confidence to validate the aircraft as safe to fly in their respective countries and regions,” the FAA said in a statement.
The move came after numerous US congressional hearings on the crashes that led to criticism of the FAA for lax oversight.
Investigators focused on anti-stall software that Boeing had devised to counter the plane’s tendency to tilt nose-up because of the size and placement of the engines. That software pushed the nose down repeatedly on both planes that crashed, overcoming the pilots’ struggles to regain control. In each case, a single faulty sensor triggered the nose-down pitch.
The FAA required Boeing to change the software so it does not repeatedly point the nose of the plane down to counteract possible aerodynamic stalling. Boeing says the software also does not over-ride the pilot’s controls like it did in the past. Boeing also must install new display systems for pilots and change the way wires are routed to a tail stabiliser bar.
American Airlines is the only US airline to put the Max back in its schedule so far, starting with one round trip daily between New York and Miami beginning on December 29.
Pilots must also undergo simulator training, which was not required when the aircraft was introduced.
Boeing’s then-chief executive, Dennis Muilenburg, initially suggested that the pilots were to blame. However, congressional investigators discovered an FAA analysis - conducted after the first Max crash - that predicted there would be 15 more crashes during the plane’s life span if the flight-control software were not fixed.
After an 18-month investigation, the House Transportation Committee heaped blame on Boeing – which was under pressure to develop the Max to compete with a plane from European rival Airbus – and the FAA, which certified the Max and was the last agency in the world to ground it after the crashes.
The investigators said Boeing suffered from a “culture of concealment” and pressured engineers in a rush to get the plane on the market.
Boeing was repeatedly wrong about how quickly it could fix the plane and when those predictions continued to be wrong, and Boeing was perceived as putting undue pressure on the FAA, Mr Muilenburg was dismissed in December 2019.
In recent weeks, European regulators have signalled their likely approval of Boeing’s work, while regulators in Canada and China are still conducting their own reviews.