On the busy day-after-Christmas travel day, Southwest Airlines canceled more than 2,700 flights, frustrating passengers across the country.
Overall, around 3,900 flights were canceled within, into or out of the U.S. on Monday, according to the flight-tracking website FlightAware.
Southwest had 2,893 flights canceled at one point Monday, or 70% of its schedule, according to the site.
On Saturday, Sunday and Monday combined, over 8,200 flights into, out of or within the U.S. were canceled, according to FlightAware.
The issue with Southwest flights also caught the attention of the Transportation Department, which called the airline's performance unacceptable.