Spokeswoman Valerie Wunder says the surcharge will protect the airline in case fuel prices rise or other costs increase.
Separately, Delta, Northwest and United have bumped the surcharge on some busy days next March to $30 each way from $20 - and to $50 on the day after the Super Bowl - according to air fare expert Tom Parsons. The airlines did not return calls immediately.
Most major U.S. airlines have been losing money this year, and they're scrambling to add revenue with bag-handling fees and surcharges on heavy travel days.
