Air Wisconsin said last week it plans to "feed" the big new United Airlines hub at Washington Dulles International Airport -- a move expected to significantly expand service between Dulles and nearby cities on the East Coast.

Starting in May, the airline, based in Appleton, Wis., will begin 20 to 25 flights a day to Dulles from four cities within a 150-mile radius. Those flights, in turn, will connect with, or feed, more than 50 longer haul flights that United said it will start operating out of Dulles at the same time.

The airline said it won't announce which cities the new flights will be serving for another two weeks, but added that they are designed to compete in the East Coast "limousine syndrome" markets -- a term used to describe cities, such as Richmond, that are serviced by airport limos or other ground vehicles going to major airports like Dulles.

The Air Wisconsin announcement quickly was hailed as further evidence of the emergence of Dulles as the region's fastest-growing airport. Principally because it is one of the few East Coast airports with room to expand, five airlines -- Pan American, New York Air, Presidential Airways, United and now Air Wisconsin -- have announced plans to expand into Dulles during the past year. Since 1982, the Loudoun County airport has more than doubled the number of passengers it serves, from 2.1 million to 4.7 million.

Equally significant, the Air Wisconsin move will help transform Dulles into a more fully competitive airport, opening up a whole new range of flights to East Coast locations, according to Tom Moor, president of the Washington Dulles Task Force, a private group of 500 local businesses that have organized to promote the airport.

"In the past, Dulles has been thought of as a long-haul airport -- good service to Europe and the West Coast, but not such good service to nearby locations," Moor said. "This helps fill in the pattern of service."

Air Wisconsin, which services 1.7 million passengers a year in 26 Midwest markets, is among the country's larger feeder carriers -- a new breed of medium and short-haul airlines spawned by airline deregulation. The key factor in its decision to move to Dulles was United's announcement last month that it would create a major "hub" with more than 50 daily departures to 24 destinations, including Boston, New York's LaGuardia, Tampa and New Orleans.

Air Wisconsin's flights will connect with those flights. Under a marketing agreement between the airlines, the Air Wisconsin flights also will be displayed as United flights on airline computer reservation systems.