Nov. 18 (UPI) -- After the longest grounding of any commercial aircraft in history, which has lasted for nearly two years, federal regulators on Wednesday lifted the ban against Boeing's 737 Max fleet to allow it to return to the skies -- as long as the planemaker makes the required changes.
The Federal Aviation Administration issued the order early Wednesday ending the flight ban, which came after the model was involved in two plane crashes in 2018 and 2019 and a lengthy regulatory review in the United States. The crashes killed a total of nearly 350 people.
The 737 Max has been out of service around the world for 20 months.
"The FAA has identified the required return-to-service activities for operators of the 737 Max and heightened surveillance and tracking of those related activities for aviation safety inspectors," the FAA said in its order Wednesday.
Among the changes ordered by the FAA are installing new flight control computer software, revising the existing Airplane Flight Manual to incorporate new and revised flight crew procedures, installing new Max display system software, changing the horizontal stabilizer trim wire routing installations, completing an angle-of-attack sensor system test and performing an operational readiness flight.
In the United States, only American Airlines, Southwest Airlines and United Airlines operate the 737 Max. Alaska Airlines has ordered some of the aircraft but has yet to operate any.
Boeing has been working since March 2019 on a fix for the model's automated flight software, a process that has been delayed by lengthy crash and oversight investigations, software development and the COVID-19 pandemic. Any return to the skies has always been contingent on a fix that was approved by the FAA.
FAA Administrator Steven Dickson said last week that an announcement detailing the necessary changes from Boeing for the 737 Max to return to service was expected "in the coming days."
The agency has previously released proposed software upgrades as well as plans for revised pilot training, and Bloomberg reported Tuesday that the FAA has already begun notifying the aviation industry of the schedule.
Now that the 737 Max is certified to fly again, the training process at U.S. carriers is expected to last for months before the plane can take off again. Southwest and United Airlines have said that likely won't be until sometime next year, while American Airlines expects it to return in late December.
The first crash, in October 2018, of an Indonesian Lion Air flight killed all 189 people aboard. Less than six months later, 157 more died in the crash of an Ethiopian Airlines 737 Max. In both cases, the planes crashed shortly after takeoff and were attributed to failures in the automated flight system.
Crash investigators later said the planes' automated flight systems were adversely activated after receiving inaccurate sensor data that put both airliners into a nose-down position from which the pilots weren't able to recover.
In September, U.S. congressional investigators concluded that Boeing prioritized profits over safety in rushing to complete the model's design before it entered service in 2017, and that the FAA provided "grossly insufficient oversight" during the approval process.
The European Aviation Safety Agency, the chief aviation regulator for the European Union, became the first major governmental regulator to endorse the 737 Max's comeback last month, saying "the level of safety reached is high enough for us."
Since the model was grounded, Boeing also hasn't been able to deliver any new 737 Max airliners anywhere in the world. In the first 10 months of 2020, Boeing lost almost 400 orders for the model.
Buoyed by news of a return, Boeing stock has climbed more than 40% so far this month, including a 4% rise on Tuesday amid optimism of imminent FAA certification. Shares remain down almost 40% for the year, however, as the COVID-19 pandemic has heavily hampered the global air travel industry.
Tuesday, the House unanimously passed a resolution requiring reforms to the FAA's aircraft certification process, a direct result of the 737 Max crashes.
