The Justice Department is investigating a number of airlines to determine whether they have violated antitrust laws through their domination of key U.S. airports.

The investigation was disclosed by Arlington-based USAir, which said its operations at Greater Pittsburgh International Airport -- where it is the dominant carrier -- have come under scrutiny.

USAir spokesman David Shipley said the government had requested information related to the investigation and that it has made similar requests from several other airlines.

The Justice Department confirmed that the investigation is focusing on more than just USAir but spokesman Joe Krovisky said the department would not identify the other airlines from which information has been requested or the cities in which they operate.

The probe into competition at certain "hub" airports comes in the wake of growing concern among policy makers about the new pattern of airline operations that grew out of deregulation.

Since the industry was deregulated in 1978, individual airlines have set up hubs -- airports that are the centers for large numbers of incoming and outgoing flights.

Although some airports are hubs for more than one airline -- for instance, Chicago, where American and United airlines have major operations -- most are dominated by a single carrier.

Several members of Congress have raised questions about whether consumers who live near hub airports end up paying higher fares than the national average.

Studies by the General Accounting Office, the Department of Transportation and others have found higher fares at hubs.

Last year, too, the Airport Operators Council International surveyed major airports, many of them hubs, and found that there were few opportunities for new entrants to establish service at most of those airports.

Several other major airlines said they had received no demand for information related to a hub investigation, although Eastern, Northwest and Continental all said the Justice Department has requested information for an existing probe into possible price fixing.

That inquiry is investigating whether collusion was involved in fare increases initiated by American Airlines in September 1989, and then quickly followed by other airlines.