Page Avjet Corp. announced plans last week for a $3 million expansion of its existing terminal facility -- which serves business and private aviation -- at Dulles International Airport.

Page Avjet President Raymond C. Moffett Jr. said the additional investment at Dulles underscored their belief that the airport would continue to grow in importance as a major air terminal serving the Washington and Baltimore metropolitan area.

Construction on the expanded facility, which will begin Oct. 18, is scheduled to be completed in November 1983. The project includes a complete remodeling of the existing facility, an additional 24,000 square feet of hangar and shop space, in excess of 14,500 square feet of new passenger lounge and executive office space, and an increase of more than 21,000 square feet of aircraft ramp and parking area.

Right now, the Page facility at Dulles has 14,000 square feet of hangar space, room for about six corporate jets on the average, according to a Page Avjet official. The new facility will house up to 20 additional planes, he said. The expansion will extend the current facility, which handles close to 200,000 passengers a year, to the north, he noted.

The company, which now employs 100 people at Dulles, said it will hire an additional 20 when the expansion is completed.

Loudon County has approved a $4 million bond to support the development of business aviation at Dulles through the Page facilities expansion, the company said.

Page Avjet, which began as Page Airways -- a civilian pilot training school -- in Rochester, N.Y., in 1938, is a diversified aviation service company that sells, services, modifies and outfits executive jet, turboprop and piston aircraft.