Southwest Airlines Inc. (LUV), the largest U.S. discount carrier, on Monday said it will eliminate 88 scheduled flights in order to boost revenue by freeing up planes for more lucrative markets.

The Dallas-based carrier estimates the schedule changes, the largest in its history, will increase annual revenue by about $60 million.

"This does represent the largest schedule tweak we've ever made," said Linda Rutherford, a spokeswoman for the airline.

Although the carrier will not replace every flight with a new one, it will replace every hour of flight time. In some cases, it might cut several short-haul flights and add one or two long-haul flights.

"In other words, we are not reducing capacity," Rutherford said.

The changes will take effect on Oct. 31.

Southwest, which has led the low-cost carrier growth in market share over the past six years, has faced increasing competition from other low-cost airlines such as JetBlue Airways (JBLU). All U.S. airlines have also been under pressure from soaring fuel prices and an inability to raise fares.

"This is the first time we have had as aggressive a look at our flight schedule in a long time," Rutherford said. "It's a sizable tweak for us. We've never done anything like this before."

The schedule changes affect 3 percent of the airlines 2,800 daily flights, Rutherford said.