Christopher Bartels, in town for an interview at the Georgetown University School of Medicine, boasted in the terminal of Dulles International Airport yesterday morning that he had just saved $30.

"From here back to Buffalo, N.Y. is $59" on People Express, Bartels said, "but it would have been $89 from BWI or National."

Bartels' savings was the result of an intense fare war between carriers that use Dulles, making it cheaper in many cases to travel from Dulles instead of Washington's National Airport.

For some passengers, according to a Washington Post survey of airlines, the battle could add up to a $100 savings on a one-way trip.

Russell Marchetta, a spokesman for People Express Airlines, which serves both airports, said the price diferences are based on simple logic: "The traffic is good out of National, but the competition is out at Dulles."

Last week's inaugural flight of Presidential Airways, which has made Dulles its headquarters, has focused new attention on the airport and the competition for passengers.

"The importance of Presidential Airways is really twofold from the standpoint of the Washington consumer," said Thomas Morr, president of the Washington Dulles Task Force, a marketing and promotion group.

He cited more frequent, direct flights to more cities as one of the major benefits. But, perhaps more important, he said, are lower prices.

"Where there's heavy competition, air fares are lower," he said. "You can see what's happening."

* People Express announced last week that it has introduced a nonstop flight between Dulles and Miami, without restrictions, for $49, until Jan. 6. The same trip on that airline from National, with connections in Newark, costs $149 during peak hours and $119 during off-peak hours.

The airline also has cut its fares to Cincinnati, Boston and Hartford.

* USAir is cutting its off-peak fares to match Presidential's prices for trips to Cincinnati, Boston, Hartford and Indianapolis. Those reduced fares will be available at Dulles, National and Baltimore Washington International Airports.

* Eastern Air Lines briefly lowered its off-peak fare between Dulles and Miami to match Presidential's $69 off-peak fare. That price goes up today, however, to $99.

An Eastern spokesman called the limited fare a traditional promotional tactic used when new competition enters the market.

* New York Air is dropping its off-peak fares between Dulles and Boston to $39, matching Presidential's fare.

New York Air, which created a Washington hub at Dulles during the summer, plans to triple its flights from Dulles by early next year. The airline also has increased the number of flights between New York and Dulles, outnumbering its flights between New York and National.

As the competition escalates, some airlines are targeting passengers who already use Dulles. New York Air has launched an advertising campaign attempting to win away customers from no-frills People Express Airline and budget-conscious Presidential Airways.

Recent full-page newspaper advertisements for the airline depict a scene reminiscent of poor immigrants awaiting processing at Ellis Island. "If this is your impression of Dulles Airport, you're flying the wrong airline," the ad states.

"Competitive actions cause you to react," explained New York Air spokesman Bruce Hicks. He said the airline is stressing services unmatched by other regional carriers at Dulles, namely passenger bridges to board planes.

Morr, of the Dulles task force, is cautious when talking about competition between National and Dulles.

"This is not a National versus Dulles question," he said, "although it could turn into that."

Presidential Airways Vice President Geoffrey Crowley pointed out that carriers at National, the metropolitan area's busiest and most congested airport, still benefit from its proximity to Washington. "Washington air travelers have tended to pay somewhat higher fares than consumers in other cities," Morr said.

"There's a feeling that National Airport is the airport of choice," he added. "The carriers there feel they can charge a premium."

But limits on the number and timing of flights out of National, increased promotion of Dulles, the opening of the Dulles Toll Road and the expansion of commuter bus services are likely to fuel growth at Dulles.

But concerns like those of Christopher Bartels about the trip from Washington to Dulles illustrate the challenge the Northern Virginia airport still faces.

Bartels said friends drove him to Dulles. "I don't think I'd fly in here if I had to get to D.C. by myself," he said.