SAN FRANCISCO (CBS SF) – The Southwest Airlines website was overwhelmed Wednesday as the airline was in the midst of a 3-day sale on air travel.

Customers saw the message, “This portion of the Southwest Airlines website is undergoing maintenance and is currently unavailable. Please try again later.”

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Screenshot of Southwest Airlines website encountering difficulties during a fare sale on June 3, 2015. (CBS)

Screenshot of Southwest Airlines website encountering difficulties during a fare sale on June 3, 2015. (CBS)

The sale, which began on Tuesday, promises one-way fares as low as $49 for flights from late August to mid-December, with the exception of Labor Day weekend and around Thanksgiving.

Some of the low-priced fares include $49 flights from San Francisco, Oakland and San Jose to Las Vegas and Southern California. Other flights from the Bay Area on sale include $99 fares to Denver and $129 fares to Chicago.

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On Wednesday, Southwest tweeted that the airline is trying to resolve technical issues.

According to CNBC, Southwest communications director Brandy King said the response to the sale “exceeded expectations,” despite adding website capacity before the sale began.

“We apologize for any inconvenience and have an intent focus on getting Southwest.com running at full speed as soon as possible. If a Customer is unable to manage their travel online, we encourage them to call 1-800-I-FLY-SWA for assistance,” King said.

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The sale ends on Thursday.