US aviation safety regulators cleared the Boeing 737 Max to fly again on Wednesday, one year and eight months after it was banned from flying.

The Federal Avation Administration — and regulators around the world — grounded the model in March 2019 following two fatal crashes.

In October 2018, Lion Air Flight 610 crashed into the Java Sea shortly after take-off, killing 189 people. Five months later, Ethiopian Airlines Flight 302 crashed on its way to Nairobi, killing 157 people. Investigations into both crashes pointed to issues with Boeing's new anti-stalling MCAS system, which tried to counter the new heavy engines' tendency to push the nose up.

The MCAS system relied on a single sensor, and pilots struggled to rectify problems with the system when they arose.

During congressional hearings, Boeing was accused of rushing the design of the plane while placing profits before safety. The FAA was criticized for a lack of oversight, leading to the approval of a flawed aircraft.

Read more: Boeing 737 MAX: Internal documents reveal staff mocking regulators, management

Following a "comprehensive and methodical" 20-month investigation, the FAA announced on Wednesday that the plane — a re-engined upgrade of a 1960s model — was fit to fly again.

However, the FAA must still approve pilot training changes for each US airline, and airlines must perform required maintenance on the planes before they can return to the sky.

Global cooperation

The FAA said the approval was made in cooperation with air safety regulators worldwide.

"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 FAA compelled Boeing to change the MCAS software, so it no longer repeatedly points the nose of the plane down and does not override the pilot's controls. Boeing must also install new display systems for pilots and change how wires are routed to a tail stabilizer bar.

The approval is a relief for Boeing, which has lost $20 billion (€17 billion) due to the saga, but it comes amid a massive, unrelated downturn in the aviation industry, caused by COVID-19 travel curbs.

Nearly 400 Max jets were in service worldwide when they were grounded, and Boeing also has a supply of 450 sitting idle. However, all of them will have to undergo maintenance and modifications before flying again, while pilots would also need to undergo simulator training.

Boeing said on Wednesday that the approval was an "important milestone."

"We will never forget the lives lost in the two tragic accidents that led to the decision to suspend operations," Boeing Chief Executive David Calhoun said in a statement. "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."

Read more: Ethiopian Airlines Flight 302: 'The pain is unbearable'

aw/dj (AFP, AP, Reuters)