Last week, reader Marilyn saw the airline ticket she purchased this summer go down in price, and I suggested some options on how she might still be able to save some money or even make up the difference in the two fares in the form of a voucher.

I want to dive into those options a bit deeper today.

For domestic airline tickets, the prevailing charge to change a ticket is $150; called the “change fee”. This fee is part of the rules of your airfare. However, there is a process, sometimes called a “rollover,” which addresses ticket prices going down on a flight (same flight) that you have already already purchased. In such cases, there are often special rules outside of the “change fee” — allowing you to typically get a voucher for the difference (you have to contact the airline, because they do not do it automatically).

Unfortunately, this “feature” on airlines that have it, is not easy to find on their websites so we did a bit of digging and found the following:

• Alaska Airlines has no fee for same flight price drops (we couldn’t find an online link but spoke with a couple of reps, evidently it is built into their online ticket change tool)
• American Airlines doesn’t have anything special for price drops outside of same day of purchase, the normal change fee applies
• Continental Airlines doesn’t have anything special for price drops outside of same day of purchase, the normal change fee applies
• Delta Air Lines¹ doesn’t have anything special for price drops outside of same day of purchase, the normal change fee applies
• JetBlue has no fee for same flight price drops (we couldn’t find an online link, but spoke with a couple of reps. Use their online change tool, or give them a call)
• Northwest Airlines offers vouchers for flight price drops, and according to reps charges a fee of $50 for the process.
• Southwest Airlines has no fee for same flight price drops (built into their online ticket change tool)
• United Airlines² has no fee for same flight price drops as long as flight meets listed criteria.
• US Airways doesn’t have anything special for price drops outside of same day of purchase, the normal change fee applies

¹Under FAQ — “If I have purchased a ticket and a new fare is introduced, can I obtain a credit?”

²Under customer service FAQ. Go to “Existing Reservations,” then “If I have purchased a ticket and a new, lower fare is introduced, can I obtain a credit?”

Lower-cost carrier AirTran has joined the ranks of the airlines that now charge a fee for checking any luggage: $15 for a first checked-bag, and it will maintain its $25 for a second bag fee.

When asked why the airline is doing this, an AirTran spokesman was blunt:

“We need all the revenue we can get.” –Tad Hutcheson, AirTran

The new fee goes into effect for new bookings, for travel on Dec. 5 or later. Those who bought tickets before today will not be charged a new fee. There is more information regarding this on AirTran’s website.