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Southwest Airlines Co. (NYSE: LUV) kicked off its huge biannual fare sale Tuesday morning, just in time for holiday traveling. With this deal, customers will be able to purchase round-trip tickets for much cheaper than previously available — try under $100 for a round-trip on dozens of routes.

The sale will span a total of three days starting early Tuesday. The travel dates covered by this sale will extend from October 31 through December 19 and from January 3 through February 14. Keep in mind that Southwest only does this sale twice a year, so now is the time to buy.

According to the deal, flights start at $49 each way on Southwest’s shortest routes, and gradually increase to $79, $99 and $129 each way for longer flights. There is some fine print in the deal, including:

Travel to Florida and Nevada and from Florida to Nevada is valid only on Sundays through Wednesdays. Travel from Florida and Nevada and from Nevada to Florida is valid only on Tuesdays through Fridays.

The sale fares from this deal specifically apply to non-stop options, although connecting itineraries will show lower-than-usual fares.

This deal has been a blockbuster in the past and is known as a staple for Southwest, which has rolled out this three-day sale each June and October for the past several years. In fact, in June 2015, this sale was so popular that it crashed the Southwest website, prompting the airline to extend its sale for an additional 24 hours.

The availability for the $49 fares appears to be incredibly broad on the surface, but these eventually will begin to disappear or sell off as more people buy into this sale. Now seems to be the best time to buy and strike while the iron is hot.