When a non-refundable fare goes down after purchase

Q:  I purchased 5 tickets from Detroit to Orlando on nwa.com 5 days ago.  When I checked Northwest site yesterday the tickets have gone down in price for the same flight number, same times and everything.  I printed a copy of their website showing the new price and submitted a claim.  Are they supposed to give me the difference or a voucher since the travel dates are not until May and the ticket prices have already dropped?

A: As far as we know, Northwest will issue you a voucher good for future travel for up to a year in the amount of the price drop, minus a $50 fee. This fee used to be $25 on domestic fares, and airlines change these price drop refund policies often.

Until a few months ago, US Air offered price drop refunds without a fee, but now they, as do many larger airlines, charge $100. Only United, Alaska, and Southwest, as far as we know, do not deduct a fee in these situations, but that too could change. We're talking here only about non-refundable tickets. If you buy full fare tickets, you always get a refund with no change fee. And the above is always assuming that there is no change in flights or days of travel. Only the fare may have changed.