If youíre planning to take a trip between Aug. 22 and Dec. 13, get your credit card ready. For the next 72 hours youíre likely to find some of the lowest fares of the year.

Southwest Airlines just announced its twice-a-year fare sale. credit: Scott Olson/Getty Images

On Tuesday morning, Southwest Airlines announced its twice-a-year fare sale, dropping prices as low as $49 each way for its shortest routes. Hereís a sample of the one-way fares being offered out of Austin: $49 to Dallas and Lubbock, $79 to Denver and New Orleans, $99 to Los Angeles and Nashville and $129 to Seattle and Las Vegas. One-way flights to Cancun start at $154.

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But donít limit your searches to just Southwest, as this fare sale typically prompts the other major airlines to drop their prices as well. I tested out an Austin-to-Denver flight on United Airlines for September dates and found one-way fares as low as $59.

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You have until 11:59 p.m. June 8 to be part of the Southwest sale.†For best results, be flexible with your dates. Some blackout dates apply.