The reason for the disruption depends on who you ask.
Southwest blamed air traffic control issues and disruptive weather in a statement issued Sunday.
That same day, however, the Federal Aviation Administration said that no FAA air traffic staffing shortages had been reported since Friday.
Southwest Airlines travelers are facing another day of disruptions. The carrier suspended hundreds of additional flights on Monday, after canceling and delaying thousands over the weekend — reportedly due to air traffic control issues and weather.
Southwest said over the weekend that the high volume of cancellations was causing longer-than-usual customer service wait times, and asked affected travelers to explore self-service rebooking options online.