Baltimore-Washington International Airport released figures yesterday showing that the airport is handily beating Dulles International Airport, its main competitor for flights and passengers.

The number of passengers using BWI in 1984 was 6.7 million, a 28 percent increase over 1983 passenger volume. The passenger level at Dulles, which was 3.5 million in the 12-month period ended Nov. 30, was 17 percent higher than the corresponding period a year before.

BWI's passenger growth rate was 14 percent in 1983 compared with the year before, and 20 percent in 1982.

BWI is owned by the State of Maryland, and Dulles is operated by the Federal Aviation Administration.

The main reason for BWI's growth spurt, said acting Maryland Aviation Administrator Nicholas Schaus, is Piedmont Airline's decision to establish BWI as one of its three "hub" airports, where numerous connecting flights are routed. Since Piedmont opened its hub there in July 1983, it has increased its daily departures from 45 to 67, and company officials have said they hope to increase the total to 100 departures a day by the end of the year, BWI officials said.

"We're quite excited by the growth," Schaus said. "We're seeing a recognition by the carriers that there's a passenger market there, and it's serving both Baltimore and Washington."

"Both airports are making progress, and both are growing at a respectable rate," said Thomas Morr, president of the Washington Dulles Task Force, a business group that promotes Dulles.

BWI's competition with Dulles was one reason Virginia and District of Columbia members of a Department of Transportation commission voted last month to name only two Maryland members to a proposed 11-member authority made up of representatives of the three jurisdictions to operate Dulles and National airports. District and Virginia officials said that because of the competition, they wanted to reduce Maryland's role in running Dulles.