CHICAGO (AP) _ United Airlines has reduced some fares substantially into December in an effort to win back business and shore up its image after a summer of labor strife, delays and cancellations.

The world's largest carrier said fares on many of its domestic round-trip flights through Dec. 14 will be reduced by about half, while long-distance U.S. and international flights be cut back less sharply.

Trying to lure more business to its Web site, United also said Tuesday that additional discounts will be given to those who book online at www.united.com.

Sample round-trip fares include Boston-Denver for $288, Chicago-New York for $198, Los Angeles-New York for $598, Washington, D.C.-Orlando $198, New York-London for $228, Denver-Munich for $448 and Chicago-Frankfurt for $508.

Discounts are available through Sept. 22. A seven-day advance purchase is required; there are no blackout dates.

Airline expert Joe Brancatelli, who writes a column for BizTravel.com, said the move reflects United's desperation at the extent of this year's problems. He said the airline gains no real advantage by launching a general fare sale, since other airlines usually match such moves.

``They must have such a gigantic shortfall in traffic, they had no other choice,'' he said.

``In August, with a 12 percent traffic decline, September and October and the whole fall must look disastrous'' for the airline, he said. ``So they had to do something drastic.''