United Airlines, which only a year ago was the world's largest carrier, on Friday said it will cut the number of flights it offers even more amid soft demand, setting the stage for additional layoffs.

The Elk Grove Township-based airline, still reeling from the Sept. 11 hijackings of a pair of its planes, said it will operate about 1,650 flights daily beginning Nov. 1, down from the 1,900 it is currently flying.

Before the attacks, United operated nearly 2,400 flights. With the additional flight reductions, United will have trimmed its schedule by 31 percent.

At the same time, the airline said it will ground its 75-plane fleet of Boeing 727s and 24 of its oldest Boeing 737s. The move will leave United with a fleet of 505 aircraft with an average of 190 seats, compared with an average of 177 seats.

Two weeks ago, when the airline announced it was reducing its schedule by 20 percent, it announced it would lay off 20 percent of its nearly 100,000 employees.

On Friday, the airline declined to comment about whether there will be further employee cuts as a result of the additional flight reductions.

United's decision to cut service 31 percent contrasts sharply with Delta Air Lines, which earlier this week said it will only reduce its winter schedule by 15 percent.

Michael Boyd, an airline consultant based in Evergreen, Colo., said the nation's airlines are in serious trouble.

"If United is cutting back, it is the first of the (next round) of cutbacks," he predicted.

Officials of American declined to comment about their fleet plans.

On Thursday, however, Donald Carty, American's chairman and chief executive, during a visit to Chicago said that if traffic doesn't build, "we're going to have to cut again."

Ft. Worth-based American also said it would lay off 20,000 and cut its capacity by 20 percent after the attacks.

American officials, while conceding the carrier is far from what it needs to break even, said about 40 percent of the seats on its flights are now filled.

Tribune business columnist David Greising contributed to this report.