In a move described as a breakthrough for Virginia's image, but a blow to Maryland's, Fairchild Industries Inc. said yesterday it has signed a long-term lease with the Federal Aviation Administration as part of relocating company headquarters to Dulles International Airport from Gaithersburg.

The announcement had been expected this week.

The move to Virginia won't have any appreciative effect on Maryland as far as taxes or loss of jobs are concerned. Fairchild will maintain its aircraft manufacturing operations and satellite and space communications divisions in Maryland.

Losing a Fortune 500 company to another state, however, "is an important loss to us," said Jerry McDonald, Maryland's assistant secretary for economic development.

Meanwhile, Jack Herrity, chairman of Fairfax County's Board of Supervisors, called the decision by Fairchild "an image breakthrough" for Virginia.

Under a 40-year lease agreement, Fairchild will construct its headquarters and marketing facility on a five-acre site adjacent to a cluster of existing office buildings opposite the main terminal at Dulles. The property will revert to the federal government at the end of the lease agreement.

A spokesman said the company expects to complete construction of the new headquarters facility within 18 to 24 months after receiving approval of building plans.

No further details or terms of the agreement were disclosed.

Edward G. Uhl, Fairchild's chairman and chief executive officer, described the company's selection of Dulles for the new headquarters site as "strictly a business decision, based on our current and projected corporate office requirements."

Uhl notified Maryland's Gov. Harry Hughes of the company's decision on Wednesday.

Although Maryland officials would have preferred seeing Fairchild retain its headquarters at Germantown, "we respect the decision of Mr. Uhl and his associates," Hughes said yesterday.

In an all-out, last-ditch attempt to persuade Fairchild to stay in Maryland, Hughes and several key members of his cabinet had met with Uhl to offer an alternative headquarters site at Baltimore-Washington International Airport. Although Maryland stopped short of offering any tax incentives, "we devoted a lot of time to making presentations designed to keep Fairchild in the state," McDonald said.

Uhl acknowledged Fairchild's appreciation to Hughes and his aides yesterday for their efforts in offering BWI as an alternative to Dulles.

Although BWI and Dulles are comparable in several aspects, Uhl said, Dulles was preferred because of the area's growth as a center of commerce, an expanding access highway system, proximity to a majority of Fairchild's corporate staff and the company's orientation toward the western region of metropolitan Washington.

Fairchild also chose the Dulles site because of rapid growth in its international operations and the need for better access to transportation, a spokesman said.