(Bloomberg) -- U.S. regulators are turning to relatively inexperienced Boeing Co. 737 pilots to help test revamped flight-control software aimed at returning the grounded jetliner to commercial service, said people familiar with the matter.

The Federal Aviation Administration wants to determine how aviators with no more than one year of 737 experience and at least one Max flight react to the software updates, said the people, who asked not to be identified because the deliberations are private. Flight-simulator testing was to begin the first week of September but was subsequently delayed a week, said one of the people.

The FAA request went to the three U.S. operators of the Max, American Airlines Group Inc., Southwest Airlines Co. and United Airlines Holdings Inc., according to Reuters, which reported the testing initiative earlier.

The FAA didn’t immediately comment, nor did Boeing or the airlines.

U.S. regulators grounded the Max in March after two crashes within five months killed 346 people.

Safety investigators have linked both crashes to a flight-control feature called the maneuvering characteristics augmentation system, or MCAS, which pushes the 737 Max’s nose down in certain situations. In June, the FAA identified a separate software problem in which the flight computer tried to lower the jet’s nose in response to a stream of erroneous data.

Southwest, the largest Max operator, has removed the plane from its schedule until early January. American and United have changed their Max schedules through early November.

--With assistance from Alan Levin and Mary Schlangenstein.

To contact the reporter on this story: Justin Bachman in Dallas at jbachman2@bloomberg.net

To contact the editor responsible for this story: Brendan Case at bcase4@bloomberg.net

©2019 Bloomberg L.P.