Who can figure airline pricing methods?

The Associated Press reports today that Delta is adding a $10 to $40 round trip fuel surcharge. Northwest and US Airways say they are studying Delta’s move. Last Friday, Northwest was the last of the big carriers to agree to a 3-to-5 percent price increase first announced by United.

Every few days, it seems, there’s another story of an airline increase so if you haven’t looked at a while, perhaps you’re steeling yourself for sticker shock.

But it doesn’t always work out that way.

A month ago, I wrote that fares were expected to go up when ATA announced it was ending its Minneapolis to Chicago (Midway) run. The Northwest fare to Midway almost doubled — from $114 roundtrip to $210 roundtrip — once the ATA competition disappeared.

However, at the time, Northwest was charging $384 for a roundtrip flight to O’Hare. Today, even after all the news reports of price increases, a roundtrip ticket to O’Hare is half of what it was a month ago ($193).