Southwest Airlines is doing it again. Right now is arguably one of the best times of the year for travelers, because airlines like Southwest are falling over themselves trying to offer the best deals and discounted fares to incentivize you to book your next trip with them. Just in the past month or so, we’ve reported on some pretty incredible offers from airlines ranging from Delta to Frontier, as well as Dallas-based Southwest which has a fare sale that, incredibly, offers flights as low as $39 one-way.

When fares are dropping to that level (and we’ve even seen some a little lower in recent weeks) it makes almost you wonder why the airline charges anything at all. At any rate, there’s a catch with Southwest’s new deals, of course — you’ve got to act fast to take advantage of this sale, as it goes away tonight.

When we say tonight, you’ve got to lock in your fare before 11:59 p.m. Pacific Time tonight. Check the fare sale page link above for the full rundown on the available deals, but as we said you’ll find that one-way flights start at $39. You can also grab some pretty sweet deals on roundtrip fares for $78 and above, while domestic flights across the US start at around $98.

Other key details to know:

  • Fares are nonrefundable, and you’ve got to buy your tickets at least 14 days before your trip.
  • Seats, travel days, and markets are limited, and blackout dates also apply.
  • For travel within the continental US, travel is valid from January 1 through May 20, 2020. For inter-island Hawaii travel, those trips can happen from January 7 through May 20, 2020. Travel to and from San Juan, Puerto Rico, is valid from January 13 through March 5, 2020, as well as April 14 through May 14, 2020. Additionally, international travel is valid from January 7 through March 5, 2020, and April 14 through May 14, 2020.

Available deals include a $95 one-way flight from Chicago to New York City; a $49 flight from Atlanta to Nashville; and a $64 flight from Los Angeles to Las Vegas.