New York CNN Business —  

American Airlines plans to cancel flights well into April because of the Boeing 737 Max grounding.

American, the world’s largest airline, said Sunday it is canceling about 90 flights a day out through April 24. Before Sunday’s announcement, American had only canceled flights through March 28.

“By proactively canceling these flights, we are able to provide better service to our customers with availability and rebooking options,” American said on its website. Customers that are affected will be contacted by American and given options for another flight.

The airline has 24 737 Max jets in its fleet. American said it is still waiting for more information from the Federal Aviation Administration, Department of Transportation, National Transportation Safety Board and other regulatory authorities before resuming flights.

The global fleet of 371 of the 737 Max jets was grounded indefinitely 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.

Other countries had already suspended the planes immediately following the Ethiopian Airlines crash.

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

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

Boeing also announced on Friday that it is cutting the production rate for all of its 737 planes from 52 a month to 42. CEO Dennis Muilenburg added that Boeing was creating a committee to review how it designs and develops jets in order to ensure the “highest level of safety.”

“We have balanced [cancellations] across our system,” said the airline. It said both international and domestic flights are affected. “We will vary by day as we look to impact the fewest number of customers.”

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

Southwest Airlines (LUV), which has 34 737 Max jets, said it is only canceling five days out at this point. It said it is also trying to rework the schedule to affect the fewest possible number of customers.

Southwest has a revised schedule through April and May that “intends to reduce drastically last-minute trip disruptions and same-day cancellations” because of the grounding of the 737 Max, a spokesman said in an email to CNN Business.

CNN’s Chris Isidore and Chuck Johnston contributed to this report.