AirTran Airways has made some changes to its A-Plus Rewards frequent flyer program.

The Orlando-based discount carrier has experienced industry-bucking growth, and as a result has toned down its popular program.

“As we get bigger, economics dictate that we can’t continue the program as rich as it is, so we’re tightening [it] a bit,” Director of Marketing Tad Hutcheson said. “There are some positives and some negatives.”

In a letter to customers mailed in April, AirTran outlined some of the changes in store.

The least popular change will probably be the increase in the number of credits required for a free ticket. It now takes eight roundtrips, when it used to take six. And though AirTran’s “offline redemptions” — a means by which customers can cash in credits for flights on other airlines — remain popular, that level has increased as well, from 12 to 16 credits.

On the plus side, the entire program is to become automated, eliminating the need for members to send in ticket receipts.

An elite level has also been implemented, allowing customers who fly 20 segments in 90 days or 50 segments in a year priority boarding and business-class upgrades. The elite status is permanent. “Once elite, always elite,” said Hutcheson.

For the first time, AirTran will introduce one-way redemptions, something Hutcheson said customers had been requesting for some time.

Also of note: a popular promotion with American Express has been tabled. The promotion, which awarded double credits for tickets purchased with the card, will end on June 30.

AirTran recently released its own Visa card through Juniper bank, but Hutcheson said that American Express had announced its intention to withdraw from the promotion before the Visa card was released.