Southwest Airlines is grappling with a wave of cancellations and delays that is stranding holiday travelers, a situation the CEO says highlights its need to modernize its operation.

While most carriers were plagued by winter storms over the holiday weekend, only Southwest was forced to cancel a majority of its trips, pointing to systemic scheduling issues that have plagued the airline for years.

The airline canceled more than 2,500 flights on Tuesday, according to data from flight tracking website FlightAware, accounting for most of the 2,900 cancellations in the U.S.