American Airlines says it has "stabilized" a computer system that failed at one of its affiliate carriers, causing the cancellation of 2,500 flights over the past week.
The failure occurred in computers used to schedule crews for PSA Airlines, which is owned by American and operates many American Eagle regional flights.
"It's a hardware issue that was causing some of our applications to run really slowly," American Airlines spokeswoman Katie Cody said Tuesday. She said employees tried to work around the problem, "but the application was running so slow they just couldn't keep up."
Tracking service FlightStats said PSA canceled more than 500 flights by Tuesday afternoon. Cody said all of the airline's morning flights were scrubbed and PSA restarted after the computer system was stabilized.
Cody said there would be some cancellations Wednesday as the airline repositioned planes and crews -- FlightStats showed about a dozen.
Many of the cancellations and longest lines since the outages began last Thursday have been at the airport in Charlotte, North Carolina, a major hub for American.
The incident highlights the role that so-called regional airlines like PSA play in the operations of the giant carriers: American, Delta and United.
Regional airlines hire their own pilots and flight attendants and contract with the majors to operate flights bearing the brands of American Eagle, Delta Connection and United Express. Some, like PSA and Alaska Airlines' Horizon Air, are owned by the big airlines, while others are independent companies.
Either way, the major airlines sell the tickets, and most passengers don't know that the flight is being flown by another airline.
Regional carriers use smaller planes, and they often fly passengers between hub airports and smaller cities. In Charlotte, PSA operates about 55 percent of the parent company's schedule -- more flights than American's own, larger planes.
The duration of the PSA outage -- six days -- and the number of canceled flights exceeded many recent technical outages at much bigger airlines. In 2016, Delta Air Lines canceled 2,300 flights and Southwest Airlines dropped more than 2,000 after separate computer outages.