Heavy traffic spurred by a fare sale has swamped Southwest Airlines’ website for a second day, leaving many customers unable to book flights.

The airline is extending the sale by one day, through Friday, to give frustrated customers more time to buy tickets.

The website problems started Wednesday, a day after Southwest announced a fall-travel fare sale. A spokeswoman says demand was heavier than the airline expected.

On Thursday morning, some customers trying to book flights online were getting a message telling them that part of the website “is undergoing maintenance and is currently unavailable.” The message directs people to call Southwest’s toll-free number, but a reporter who did that got a busy signal.

(AP)