New York (CNN Business) American Airlines now won't use its fleet of Boeing 737 Max planes any time this summer.

The world's largest airline, which has 24 of the 737 Max jets in its fleet, said it is canceling about 115 flights a day through September 3 as a result of the grounding. It previously had canceled flights through August 19. The plane was grounded in mid-March after two fatal crashes , putting focus on a particular safety feature on the plane.

Southwest LUV United Airlines' UAL American's canceled flights are the most extensive among US airlines., which has 34 of the 737 Max jets in its fleet, has canceled flights only through August 5 at this time. cancellations also run into August.

American AAL Not all of the American flights scheduled to be flown by the 737 Max will be canceled outright. Some will be flown with other aircraft.is also canceling some flights scheduled to be flown by different aircraft, such as the original 737, to shift those resources to other flights.

American said it is adjusting its schedules to affect the fewest number of passengers possible, and passengers whose flights are canceled will be able to rebook at no cost or get a full refund if they don't wish to take their trip.

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