American Airlines has canceled more than 1,500 flights since Friday, blaming staffing problems and high winds at its busiest hub several days earlier. It’s the latest mass flight disruption to face travelers as some carriers struggle to handle a rebound in travel demand.

The cancellations increased at the end of the weekend. On Sunday, American canceled about 667 mainline flights, nearly a quarter of its mainline schedule, according to flight-tracking site FlightAware. Dallas-based Southwest Airlines cut 185 flights, or 5% of its Sunday operation.

American canceled some 340 flights on Friday and 543 flights, or 20% of its schedule, on Saturday.

American’s COO David Seymour said in a staff note on Saturday that the problems started with high wind gusts on Thursday that cut capacity at its Dallas/Fort Worth International Airport hub and that crew members ended up out of position for their next flights.

Pilot and flight attendant availability were listed as reasons for most of the cancellations on Saturday and Sunday, according to internal tallies, which were seen by CNBC.