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Southwest Airlines won’t be using its fleet of Boeing 737 Max planes for the entire busy summer travel season.

The Dallas-based carrier announced it has canceled flights scheduled to use the grounded aircraft through September 2. Southwest has 34 of the 737 Max planes in its fleet, the most of any US airline.

“By proactively removing the MAX from scheduled service, we can reduce last-minute flight cancellations and unexpected disruptions to our Customers’ travel plans,” the airline said in a statement.

Southwest will contact customers on flights that were scheduled to use 737 Max planes, and the airline will offer them alternative travel options. The change will cause roughly 100 daily flights to be removed from the scheduled, which is less than 3% of Southwest’s normal amount of daily flights.

“We offer our apologies to our customers impacted by this change, and we thank them for their continued patience,” it added.

Southwest, and other airlines, are awaiting a fix from Boeing for the 737 Max. The plane was grounded worldwide in mid-March after two fatal crashes. Boeing is seeking to win approval from the FAA and international regulators for a software fix that is designed to address the automatic safety feature that is the focus of the crash investigations.

Summer is one of the busiest times of the year for air travel, so the lost flights will hurt the airlines. Boeing is expected to find ways to compensate airlines hurt by the Max grounding.

Earlier this week, American Airlines said it was canceling about 115 flights a day through September 3 as a result of the grounding. The world’s largest airline has 24 of the 737 Max jets.

Similar to Southwest, American said it is adjusting its schedules to affect the fewest number of passengers. Those 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.

Boeing is continuing to face difficulties in light of the grounding. The company reported Wednesday no new commercial aircraft orders in May — the second straight month that Boeing’s orders were at a standstill in the face of the 737 Max crisis.

The drop in orders isn’t only because of the grounding of the 737 Max. Boeing also has a massive backorder of about 5,000 planes. Many of its customers do not need to place orders for additional jets right now.