Delta Air Lines, the No. 3 U.S. carrier, said it raised fares $5 each way on flights within the continental United States, in the latest effort to offset rising costs.
Strong demand has given U.S. airlines leeway to raise fares over the last year or so, helping them post profits after years of losses.
But recent attempts to raise fares have largely been unsuccessful. U.S. carriers, meanwhile, face rising maintenance and labor costs, and jet fuel prices remain at historically high levels.
Delta's move marks the fourth effort to increase air fares this year. The two most recent attempts were mostly rescinded after rivals didn't match.
"While increases so far this year have had a hard time sticking, this one may have greater success than the previous efforts," said Neil Bainton with air fare research firm FareCompare.com.
Demand for air travel generally picks up as the weather warms.
AMR's American Airlines and Northwest Airlines said they were looking into Delta's fare increase, but didn't say whether they would match. UAL's United Airlines and Continental Airlines didn't immediately comment.