WASHINGTON (AP) — Airlines are having trouble hiring pilots, flight attendants and other personnel, and that's part of what is causing canceled flights and scrapping of service to some airports, executives told legislators on Wednesday.

American Airlines CEO Doug Parker said a large service outage in October began when high winds shut down three of five runways at Dallas-Fort Worth International Airport, the airline's largest hub.

American, he said, ended up with jets and people in the wrong places, and had a hard time getting workers to pick up extra shifts to handle the problem.

Although workers are doing a great job during the pandemic, they are reluctant to take extra shifts due to the risk of the novel coronavirus and unruly passengers, he said.

"We need people to want to pick pick up additional shifts," Parker told the Senate Commerce, Science and Transportation Committee. Parker said there are enough pilots and staff to run the airline under normal circumstances, but not with surprise weather events.

United Airlines CEO Scott Kirby said they have to make sure they don't schedule too many flights for the available resources.

He said people who want to be pilots have to spend $150,000 to get the required training, which typically is not covered by federal student loans.

Kirby, Parker and leaders of Southwest and Delta all said they're taking steps to train more pilots.

Under questioning, John Laughter, chief operating officer of Delta Air Lines, said Delta has had to end some flights due to a shortage of pilots for regional jets that serve less-populated areas. He sees recovery coming next year.

Southwest CEO Gary Kelly said federal mask requirements for airline passengers "don't add much if anything" because most planes have HEPA air filters and turn over the cabin air.

They spoke during a hearing on airlines getting $54 billion in aid from taxpayers to keep employees on the payroll during the pandemic. All said the money saved jobs and businesses and made it possible to recover quickly once air travel rebounded.