American Airlines (AAL) - Get Report -- the world's largest airline -- has yet again pushed back the lift off date for 737 MAX jets, now telling passengers the beleaguered Boeing  (BA) - Get Report jet will remain grounded through Sept. 3, missing most of the summer travel season.

"By extending the cancellations, our customers and team members can more reliably plan their upcoming travel on American," said the airline Sunday in a statement.

Around 115 flights will be canceled daily for the airline while the jet is grounded.

The airline said, however, that it "remains confident" that software updates and new training under development will allow the aircraft to become certified again.

As the airline works with the Federal Aviation Administration, Department of Transportation, National Transportation Safety Board, and other regulatory authorities, it said, it's "pleased with the progress to date."

Yet, American had already held off giving the green light for the jet, and in April had extended grounding the MAX through Aug. 19. 

American, the world's largest airline by several measures, has a fleet of 24 Boeing 737 MAX aircraft.

Controversy has surrounded Boeing's new jet since one crashed in March in Ethopia, killing all on board, and another went down over Indonesia in October, also killing everyone on the jet.