Editor’s Note: A previous version of this article indicated Southwest had canceled all departing flights from Los Angeles area airports until Dec. 31. While many flights are canceled or delayed, the airline says only booking is largely “unavailable” until Dec. 31.

What began as a crisis for Southwest Airlines amid a crippling winter storm turned to paralysis Monday evening when the budget carrier canceled many departing flights from Los Angeles area airports.

At LAX, most Southwest flights were listed as canceled or delayed Monday and again on Tuesday, and attempts to book through the airline’s website produced “unavailable” messages until Dec. 31.

Similar issues were reported at the San Diego International Airport.

Southwest assured travelers, however, that planes are still flying.

“Inventory available to book flights across our Network is very low – and nearly all flights currently show unavailable on Southwest.com – but we are still operating flights,” Chris Perry of Southwest Airlines said.

Nationally, approximately 2,700 Southwest flights were canceled Monday and another 2,600 -around 63%- were canceled Tuesday, according to FlightAware.com. 15% were listed as delayed.

Tirso Rayo was at LAX Monday evening, trying to make a flight back home to Boise, Idaho. Their flight was canceled, and rescheduling seemed unlikely.

“They don’t care,” Rayo said. “It’s poor business, never again will I ever fly with these guys.”

Others opted to take the long way home by renting vehicles and carpooling.

The operational issues plaguing Southwest come after one of the busiest travel weekends of the year and right in the middle of the winter break travel rush.

Long lines both in person and on the phone have left travelers frustrated, exhausted, and helpless without much information.

A purported internal memo leaked by an employee Monday blamed some of the operational crisis on employees calling out sick. Southwest has not commented on the veracity of the document.

Southwest has apologized for cancelations which it has called “unacceptable.”

“With consecutive days of extreme winter weather across our network behind us, continuing challenges are impacting our Customers and Employees in a significant way that is unacceptable,” Southwest said in a statement Monday. “And our heartfelt apologies for this are just beginning.”

The United States Department of Transportation said it would be investigating the rate of cancellations and delays to determine if they were preventable and whether or not Southwest is “complying with its customer service plan.”

Transportation Secretary Pete Buttigieg also said he was monitoring the situation closely and said we would have more information on Tuesday.