United Airlines has joined carriers announcing additional flight cancellations as problems with the Boeing 737 Max aircraft extend into the peak summer travel season.
Chicago-based United said Monday it would pull flights on the 737 Max from its schedule through early July. American Airlines and Southwest Airlines had already announced plans to extend cancellations into August.
Regulators around the world grounded Boeing's 737 Max last month after the plane was involved in deadly crashes in Ethiopia and Indonesia. Boeing is working on a software fix for the plane, but regulators will need to sign off on the plane's safety before it can begin flying again.
United said it had been using spare aircraft and other "creative solutions" to cover flights that would typically use one of the grounded aircraft. But those changes are harder to make during the busy summer season, United said in a statement.
"We'll continue to take extraordinary steps to protect our customers' travel plans," United said.
United said it expects to cancel about 130 flights in April because of the 737 Max grounding.
American, which uses more 737 Max jets than United, said it would cancel about 115 flights per day through Aug. 19, or about 1.5 percent of its flights.
Canceling flights lets the airline "plan more reliably for the peak travel season," airline executives said in a letter to employees Sunday.
The number of flights canceled at O'Hare International Airport could change day-to-day because the airline makes adjustments to try to affect the smallest number of customers, said American spokeswoman Leslie Scott. That means the airline might operate a flight scheduled to take place on a 737 Max by substituting another aircraft, or cancel a flight not scheduled to use that aircraft.
American has begun notifying passengers whose flights have been rebooked, Scott said. Customers who choose not to fly on a new itinerary can receive a refund.
United and Southwest also said they are reaching out to customers rebooked because of 737 Max-related cancellations.
After initial disruption when the 737 Max was pulled from operation last month, Lynn Farrell, president of Windy City Travel, said the aircraft's extended grounding wasn't as problematic as travelers might assume.
The 737 Max cancellations still account for a tiny fraction of all flights, said Scott Mayerowitz, executive editorial director of frequent flyer website The Points Guy. But travelers could start to feel more of an impact as flights grow fuller during the busy summer travel season.
"Planes are packed solid and it's not like airlines have a lot of jets just sitting around to throw on different routes," Mayerowitz said.
Even when an airline can avoid canceling a flight by swapping in a different aircraft, it won't necessarily have the same layout. That means the airline might shift passengers' seat assignments, a problem for families trying to sit together or passengers who chose a seat with more legroom, Mayerowitz said.
Travelers concerned about keeping a chosen seat can check their reservations before arriving at the airport. While there are no guarantees an airline will accommodate a request to change seats, it's worth asking, he said.
Airlines are having to extend contingency plans for the 737 Max's grounding as Boeing continues to work on software that will make changes to a flight-control system that was erroneously activated in both crashes, along with additional training for pilots.
American said it's confident the software updates and new training will allow regulators to re-certify the jet before mid-August.
Once it is deemed safe and ready for takeoff, Farrell said she would have no qualms about booking clients on it, or flying on it herself.
"Once it gets back up there, it will probably be the most scrutinized airplane ever flown in the skies," she said.