Southwest Airlines (NYSE: LUV) is raising rates on about 10% of its routes, by $5 each way. Raising prices in September could be a good move because business travelers tend to be the customers between September and February, and they have less flexibility than those traveling for pleasure.

After Southwest announced the fare increases, United Airlines, American, Delta Air Lines, JetBlue Airways, Virgin America, and US Airways followed suit. United expanded the increase to all domestic routes except for Hawaii, according to reports. 

A spokesman for Southwest cited higher fuel costs as the main reason for the increase, according to a USATODAY report. Crude oil is trading right around $100/barrel, up significantly from its $78 low in June.

Fool contributor John Divine owns no shares in any of the companies above. You can follow him on Twitter @divinebizkid and on Motley Fool CAPS @TMFDivine.

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