(Bloomberg) -- Southwest Airlines Co. is weighing another delay for the return of the 737 Max to its flight schedule as Boeing Co.’s grounded plane awaits approval by aviation regulators.

The airline probably won’t be able to use the Max by the planned date in early March if the flying ban isn’t lifted this month, Chief Executive Officer Gary Kelly said Thursday. While Southwest has yet to make a final determination, Kelly said the current schedule is at risk after the Federal Aviation Administration this week highlighted the remaining hurdles in the re-certification process.

“We’ll continue to guess when the Max will be available to us to put back into revenue service,” Kelly said in an interview at Bloomberg‘s New York headquarters. “If they can’t get the airworthiness directive to return to service this month, it will make it hard for us to make March 6.”

Southwest, the largest Max operator, and the two other U.S. carriers that have the plane recently scheduled the Max to resume service in early March, pushing back previous plans. Once the FAA approves the plane to resume flying, customers will need several weeks or months for pilot training and other preparations to return to commercial service.

Boeing’s top-selling jetliner has been grounded since March after two fatal crashes.

To contact the reporters on this story: Mary Schlangenstein in Dallas at maryc.s@bloomberg.net;Richard Clough in New York at rclough9@bloomberg.net

To contact the editors responsible for this story: Brendan Case at bcase4@bloomberg.net, Tony Robinson

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