Airfares have been noticeably more expensive lately [1], but a few airlines have put a pause in that trend by launching a round of fare sales this week. Southwest, AirTran, and Frontier announced prices under $100 [2] on several shorter routes.

The deals won't last long — most tickets need to be purchased in the next couple days — but they are certainly worth checking out. For details on some of the deals to be had, .

• Southwest: Two-day sale with fares of $30 each way on flights of 400 miles or less; $60 one-way fares for flights between 401 and 750 miles; and $90 one-way for longer trips. These prices aren't available for travel on Fridays and Sundays, and seats for travel between Sept. 9 and Nov. 18 are limited.
• AirTran: Fares as low as $39 each way for some short routes from mid-July through Nov. 11. You'll find the lowest prices for travel on Tuesdays, Wednesdays, and Saturdays. Tickets at these low prices are available through Thursday, July 9.
• Frontier: Sale covers travel from Aug. 10 through Jan. 15, but blackout dates apply around the Dec. holidays. The airline's sale is longer than the others, with a deadline of Tuesday, July 14 for buying tickets.