The airline's fare hikes of as much as $10 each way were quickly matched by American, Continental, Northwest and other major U.S. airlines.
Nearly 70 percent of Southwest's routes were affected by the fare increase, USA Today reported Tuesday.
Southwest -- the only carrier to report profits in every quarter since the Sept. 11, 2001, attacks -- earned $57 million in 2006's fourth quarter, down from $70 million in the year-earlier period.
JP Morgan airline analyst Jamie Baker said he expected "a full-court press for higher revenue" from Southwest, with the rising-fare trend probably lasting several years due to "rising labor and fuel costs."
Southwest's top fare now is $339 one way for a coast-to-coast flight, compared with $299 in January 2005.
This is still lower than the nearly $700 full price one-way coach fare most traditional carriers charge, Bestfares.com Publisher Tom Parsons said.