JetBlue Airways Corp., which offers free in-flight e-mail and television, will charge $10 to $20 more for certain seats with extra legroom in an effort to increase revenue.

Six rows on the Airbus SAS A320 planes will have 38 inches of legroom, four more inches than on regular seats, the New York-based carrier said Wednesday. The fees vary from $10 to $20, based on the length of the flight.

JetBlue and other airlines are trying to find ways to boost revenue and cut costs as fuel expenses surge and a foundering U.S. economy restrains demand. Northwest Airlines Corp. charges $15 or more for certain spacious exit-row and aisle seats, and AMR Corp.'s American Airlines has added back many of the thousands of seats it had taken from planes to increase room.

As many as 36 seats, or one-quarter of all spots on each of the A320 planes, will have more legroom, JetBlue spokeswoman Alison Eshelman said.