CNN  — 

American Airlines is extending flight cancellations into early June because of the Boeing 737 Max grounding.

American (AAL), the world’s largest airline, said Sunday it will cancel about 90 flights daily through June 5. American (AAL) had previously canceled flights through late April.

The airline is hopeful that that the 737 Max planes will be flying again soon, but said it is canceling flights about a month out as it waits for word from the Federal Aviation Administration.

“Canceling in advance provides additional availability and rebooking options for our customers,” said the statement from American.

Boeing’s 737 Max planes were grounded indefinitely in the United States on March 13 after two of the planes had fatal crashes. A Lion Air flight crashed in October and an Ethiopian Airlines flight crashed on March 10.

The causes of the crashes have yet to be determined, but the focus has been on an automatic safety feature that may have forced the nose of each plane lower when it incorrectly believed the plane was in danger of going into a stall.

Boeing (BA) and the FAA said they are working on an upgrade of the 737 Max software to deal with that safety feature. Boeing (BA) said at the time of the grounding that it expected that update to be available “within weeks.”

American has 24 of the 737 Max 8 jets. But not every flight which had been scheduled to have a 737 Max has been canceled. American said it has rearranged its schedule to use other aircraft to complete some of those flights.

American operates 3,300 flights its mainline system daily on average, and another 3,400 through regional carriers and partner airlines.

Other carriers are not canceling nearly that far out.

Southwest Airlines (LUV), which has 34 737 Max jets, has also said it is canceling flights and will not return them until service until authorized by the FAA.