Southwest Airlines Co. will keep the Boeing Co. 737 Max out of its flight schedule at least through Oct. 1, a month more than previously planned, as safety regulators debate when the grounded aircraft will be approved to resume operations.

The extension will force the continued cancellation of 150 daily flights, Southwest said in a statement Thursday. The Dallas-based carrier, the biggest customer of the Max, made the decision just two weeks after delaying the plane’s expected return to early September from a prior plan of early August.

Southwest is extending the Max’s absence again as the Federal Aviation Administration grapples with a new safety risk on Boeing’s best-selling jet, which was grounded worldwide March 13 after two fatal crashes in five months. While the airline said it made the scheduling decision “before any developments of the past few days,” the new problem spurs further uncertainty on when safety regulators will let the single-aisle workhorse return to the skies.

“We remain confident that, once certified by the FAA, the enhancements will support the safe operation of the Max,” Southwest said in the statement.

Boeing Fixes

Boeing is crafting software fixes and enhanced pilot training for the plane.

American Airlines Group Inc. and United Continental Holdings Inc. have set the Max to return to their schedules around Sept. 3.

In a finding unrelated to the cause of the crashes, the FAA determined that data processing by a flight computer could cause the Max to dive in a way that pilots had difficulty recovering from in simulator tests, Bloomberg News reported.

The issue didn’t involve the Maneuvering Characteristics Augmentation System, which has been linked to the disasters involving Max planes operated by Indonesia’s Lion Air and Ethiopian Airlines.

Boeing is looking at a potential “end of summer” return for the Max, and getting the entire grounded fleet back into the air will take months, Chief Executive Officer Dennis Muilenburg said Wednesday.