There are, of course, still many markets where Southwest is indeed the lowest-priced carrier, and many where Southwest has forced rival airlines to drop their prices. Historically, there have always been instances where other airlines had cheaper prices than Southwest for particular flights. But travelers and fare analysts say that as Southwest has pushed its prices higher, that's happening more often.

"Southwest is becoming more of a hybrid, catering more to the business traveler and acting more like a 'big' airline," said Robert Harrell, a consultant who tracks airfares weekly. An upside of higher airfares: They help business travelers earn more points in Southwest's revamped frequent-flier program, which entices people to pay higher prices to get bonus points.

Craig Seidel of Palo Alto, Calif., flies Southwest frequently between San Jose and Burbank for work and has seen one-way ticket prices go from $69 Wal-Mart levels to seemingly Nordstrom levels of double or triple the price.