Boeing's 737 MAX completes recertification flights

The Federal Aviation Administration announced Wednesday that Boeing's 737 MAX completed a crucial phase of its recertification process — namely, test flights.

"During three days of testing this week, FAA pilots and engineers evaluated Boeing’s proposed changes in connection with the automated flight control system on the aircraft," the agency said in a statement. "While completion of the flights is an important milestone, a number of key tasks remain, including evaluating the data gathered during these flights."

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The global fleet of 737 MAX planes has been grounded since March 2019 after two fatal wrecks that left 346 people dead.

Related: Lion Air initially wanted simulator training for 737 MAX pilots, documents show.

The flight control system that the FAA mentioned in its statement is suspected of contributing to both crashes. The system, known as MCAS (Maneuvering Characteristics Augmentation System) was created to make the MAX fly more like earlier versions of the 737, despite the latest update having larger engines that were mounted farther forward than on its predecessors. The system was meant to ease pilot training requirements for airlines that had older versions of the 737 in their fleets.

It could still be a few months before the MAX is cleared for commercial service in the U.S. again, and it also remains unclear if foreign regulators will accept the FAA's recertification as they have historically, or if they will try to do flight testing of their own.

Related: Here’s what Boeing’s next moves say about the slow resumption of travel.

Boeing's relationship with the American regulator has come under scrutiny in the wake of the MAX crashes, and critics have said that the FAA was too deferential to the manufacturer.

As Boeing and global authorities have prepared for the MAX to reenter service, Boeing and the FAA have taken pains to assure the public that the regulator is in charge and autonomous in its decision to allow the aircraft to fly again.

Related: American Airlines to keep Embraer E190s longer amid Boeing 737 MAX uncertainty.

The FAA said remaining steps to recertification include finalizing recommendations for pilot training from the agency's Flight Standardization Board and the Joint Operations Evaluation Board, which includes input from other global aviation regulators. After that happens, a series of paperwork steps are required, and ultimately the FAA will re-approve each airline's pilot training regimen for the 737 MAX before individual companies can bring their aircraft back into service.

Read more: The 737 MAX mess — a timeline of how we got here.

In the U.S., American Airlines, United Airlines and Southwest Airlines are the primary operators of the aircraft, with Southwest having the most MAXes in its fleet. Before it was grounded, the MAX was Boeing's best-selling jet, but airlines have been scaling back their orders. At one point, Boeing even temporarily shut down the production line as it was running out of places to store finished, undelivered airframes. The grounding also left airline schedules in flux for months, though that problem has been overtaken by the coronavirus demand slump.