I don't understand. Are you talking one way or round trip?

Normally 16 credits gives you a coach round trip ticket. These are capacity controlled and on resort destinations often are used up quickly. You may also book a business class rewards ticket for 16 credits each way. These are also limited but are far more available.

It is possible that A+ Rewards tickets will reappear, it seems they regularly do on Southwest, but I've seldom seen it on Airtran. The resort destination also makes it less likely.