Boeing's 737 MAX is one step closer to carrying passengers again

A Boeing 737 MAX took to the skies over Washington Monday, marking a major, tangible step toward the plane eventually being returned to commercial service.

The Federal Aviation Administration confirmed it is working with Boeing on a series of recertification flights that are a crucial part of clearing the MAX to again fly scheduled airline service.

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The global fleet of Boeing's best-selling narrowbody jet has been grounded since March 2019 after two fatal crashes that together killed 346 people.

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

Monday's flight lasted slightly more than an hour, according to FlightRadar24, and the FAA said it is the first in a series that will take place over about three days.

The flights, the FAA said, "will include a wide array of flight maneuvers and emergency procedures to assess whether the changes meet FAA certification standards."

It's expected that the tests will put particular emphasis on updates to an automated flight control system that contributed to both of the fatal accidents that led to the grounding.

Related: Alaska Airlines calls Boeing a ‘fantastic partner’ as it decides between A321neo and 737 MAX.

Boeing and the FAA have come under scrutiny in the wake of those crashes for what critics have called a close relationship and for deference the FAA had paid to the manufacturer when the plane was originally certified. As the plane's recertification has drawn closer, both organizations emphasized that the FAA is taking the lead throughout the process and that it is being thorough in its analysis and testing of changes to the MAX.

Review: Southwest (737 MAX 8) Inaugural Flight From Dallas to Houston.

"While the certification flights are an important milestone, a number of key tasks remain," the agency said in its statement. "The FAA is following a deliberate process and will take the time it needs to thoroughly review Boeing’s work. We will lift the grounding order only after we are satisfied that the aircraft meets certification standards."

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

Industry watchers have predicted that the MAX could be cleared carry passengers again as soon as this fall, but the timeline remains fluid, pending the outcome of tests and approval of other related measures like new training protocols for pilots.

Before it was grounded, the MAX was Boeing's best-selling jet, and was poised to become a workhorse for airlines around the world. It's still likely to become a crucial part of many fleets, though on a slower schedule than predicted a few years ago. In the U.S., Southwest Airlines, which operates an all-737 fleet, was the largest operator of the jet before the grounding, and American and United also have some on their property already. Both Southwest and United have announced plans to reduce their 737 MAX orders.