Tech glitch delays hundreds of Southwest flights

A technology glitch delayed hundreds of Southwest Airlines flights Sunday while the airline checked-in passengers manually at airports.

"We're experiencing intermittent technology issues on Southwest.com, the Southwest Mobile app, and in reservations centers and airports across our system today," the airline said in a statement. The airline asked that fliers arrive at least two hours prior to their scheduled departures to help minimize delays.

About 300 flights had been delayed as of early Sunday afternoon, the Dallas-based airline said.

In Los Angeles, airport police tweeted a photo of long lines at the Southwest desks with the warning to "avoid delays arrive early."

One passenger, waiting in line just before noon outside Nashville International Airport, tweeted that the Southwest line was "Crazy long — can't even see the end! Hold flights plz!"

At Denver International Airport, Emily Mitnick, said she missed her 10 a.m. flight to Detroit, even though she parked her car around 8 a.m. She estimated that about 1,000 people were online at the check-in for a boarding pass.

"The clock was ticking and the flight took off," Mitnick told the Associated Press.

The Southwest check-in line at McCarren International Airport in Las Vegas wrapped around the building and down the street, Ida Perez told NBC News. Perez said she waited in line for over two hours before finally making her flight.

The technical glitch is the latest to disrupt the nation's airline service in recent months. American Airlines blamed a computer failure for halting flights to three major hubs for for a two-hour window on Sept. 17. And nine days earlier United Airlines' website crashed for more than two hours, forcing passengers to check-in via mobile apps or airport kiosks. A computer glitch in July grounded many United flights for nearly two hours, snarling the airline's schedule nationwide and creating long lines at airports.

Southwest, which had 3,600 flights schedule Sunday, said it was working to fix its problem.

"While teams work diligently to enhance the performance of our technology, our airport-based employees are working with customers on their individual itineraries and we apologize for the extra effort and delayed arrival of passengers and their baggage," the airline statement said.

The airline warned passengers flying Monday to arrive two hours early and print boarding passes before coming to the airport.