Deal originally posted April 22, 2012. Deal ends November 1, 2014. Post updated 10/13/14:

Southwest Airlines and Airtran Airways' three-year merger is almost complete. For over two years, transfers have been allowed between Southwest's Rapid Rewards loyalty program and Airtran's A+ loyalty program.

These transfers present an arbitrage opportunity that caps roundtrip award flights at 19,200 Southwest points (the normal cost of a $274 award.)

This is a cool trick that can save you major Rapid Rewards.

Three weeks ago I got an email from AirTran A+ Rewards with the subject "Get 750 Rapid Rewards Bonus Points."
The email explains that Rapid Rewards and A+ Rewards, Southwest's and AirTran's loyalty programs will merge on November 2, 2014. (Southwest acquired AirTran in May 2011.)
If you verify your A+ and Rapid Rewards accounts to make that combination easier on the airline, you can get a quick 750 Rapid Rewards, worth about $11 in free flights.

According to this thread on FlyerTalk, Southwest Airlines has started to display bookable AirTran flights on its own website. The first AirTran city pairs offered on Southwest.com are Atlanta <-> Fort Lauderdale and Atlanta <-> Fort Myers. A sample screenshot of the newly available flights is below.

These flights are still bookable on AirTran's website.

Joanne writes:

"I have accumulated approximately 55,000 Southwest Rapid Rewards. I see that I have a Southwest flight credit that is expiring, and Southwest wants me to use 18,000 points to create a reward flight. I have my eye on a roundtrip award to Phoenix that costs 29,000 points. Is it worth it to do this? I am so confused. Any help is appreciated."

I can sympathize with Joanne's confusion.