Southwest Airlines low-fare, 72-hour sale is on!

Houston Hobby // Stephen M. Keller, 2018 (Photo via Southwest Airlines)

The big Southwest Airlines sale is back!

They're holding a 72-hour sale in which some round-trip tickets cost just $100.

Southwest Airlines holds this three-day sale twice a year, and they just launched the latest one Tuesday morning.

One-way fares start at $49 and go up to $129 for longer flights.

The sale is good for domestic travel between August and December of this year, but you can't travel on Fridays and Sundays.

For international travel destinations and Puerto Rico, the dates vary.

If you're ready to get out of town, you have until Thursday to book and get a deal.