Southwest offers 72-hour fall fare sale starting at $49

For 72 hours only, Southwest Airlines is offering a fall fare sale with one-way nonstop flights starting at $49.

The sale is for select destinations and fares depend on the mileage of your trip. For travel up to 500 miles, fares are $49 one-way. For travel 501 to 1,300 miles, fares are $99 one-way. For travel 1,301 or more miles, fares are $139 one-way.

Travel must take place between Aug. 13 and Nov. 14 (Darn. There goes Thanksgiving). And sale fares are available every day except Fridays and Sundays. (There goes that weekend getaway plan.) There are also a few blackout dates around Labor Day. Customers must purchase the flights by 11:59 p.m. PST Thursday.

Airtran, a subsidiary of Southwest, is also offering a parallel sale with fares starting at $49, $99 and $139 each way. Fares are nonrefundable and AirTran charges a $75 change fee so be absolutely certain before you purchase.

Southwest offers this mileage-based deal about once a year. It's interesting to note that in 2010, a similar sale featured one-way fares for $39, $79 and $119. So it's gone up a few bucks. But note that back then you would pay the highest fare on flights of more than 1,001 miles. That's 300 fewer miles than today's sale allows for. So if you traveled the very same 1,001 miles, you would actually pay less today than two years ago.