LINTHICUM, Maryland: Once, when USAir was one of the 'big four' airlines, BWI airport in Maryland was practically a private operation, with more than 70 percent of its daily flights handled by the airline. Now, USAir is USAirways, and that number is 45 percent and falling. The airline has informed its employees that as many as 220 workers at BWI, or one fourth of the 860 full-and part-time gate workers, ticket agents and mechanics, will be laid off as USAirways continues a cost-cutting reorganization of its hub system by routing more flights through Philadelphia. The moves are an attempt to continue the remaking of US Airways into the giant it once was and not the bloated behemoth that did not have a profitable year between 1988 and 1995. Since Stephen M. Wolf was elected chairman in early 1996, however, USAirways has been on something of a warpath. One of Wolf's first moves was to order up to 400 new Airbus jets, one of the largest orders in history. Within two weeks he had changed the name to US Airways, heralding it as a "commitment to be the carrier of choice." The silver-and-blue makeover is having the desired effect. Profits and passenger levels are inching steadily back up, and the airline currently stands at fifth-largest. But for the gate workers, the ticket agents and the mechanics at BWI, the turnaround is exacting a painful price.