We got indications late last week that Southwest had initiated air fare increases, and over the Labor Day weekend, FareCompares technology got wind of other activity, which was the other major domestic airlines matching Southwest, on those routes that overlap the carriers.

These increases are based on the number of miles traveled. Increases you can expect on one-way flights of varying lengths:

• $1 for one-way trips less than 500 miles
• $3 for one-way trips less between 500 and 1000 miles
• $5 for one-way trips between 1000 and 1250 miles
• $5 and $10 for one-way trips over 1250 miles

To put this in context, the number of miles between Chicago and Los Angeles is 1757. Plus, these increases include business (less than 14-day advance purchase) and leisure travel.

Who’s following this lead? American Airlines, United Airlines, US Airways, Continental Airlines, Northwest, Frontier, Alaska Airlines and, to a lesser extent, Delta. The story has caught the attention of the media, and I was contacted and asked to comment on it by reporters.

It’s always amazing to me how you can have an in depth interview, and one random quote gets pulled from it. Check out the story in the Baltimore Sun (via Bloomberg) to see what I mean.

As for the Southwest move; is it unusual activity for this time of year? You bet. But these increases are significantly smaller than normal, system-wide increases. Still, it’ll be interesting to see how it all shakes out and what it’ll mean (if anything) for the upcoming holiday season.