A few years ago, the idea of operating a flight between New York's Kennedy International Airport and Dulles International Airport outside Washington seemed preposterous.

Now, two airlines are planning service.

Delta Air Lines

( DALRQ) will fly three times a day starting July 5, using 37-seat Dash 8 aircraft.

JetBlue Airways

(JBLU) - Get Report

will fly six times a day starting Aug. 17, using 100-seat Embraer 190 aircraft.

The nine new flights are evidence of the rise of the two airports, once considered too far from business and population centers served by closer-in airports -- LaGuardia in New York and Reagan National in the nation's capital.

Today, Kennedy is the country's eighth-busiest airport with 41 million passengers annually and two hubs. Delta has 165 daily departures from Kennedy, while JetBlue will have 133 daily departures to 34 destinations after adding Jacksonville, Fla., service on Thursday.

AMR

(AMR)

unit American Airlines has about 100 daily departures from Kennedy and says it plans to further expand.

Meanwhile, Dulles, which serves a growing business market and population in northern Virginia, is the 20th-largest airport with about 27 million passengers annually.

UAL's

( UAUA) United Airlines has a long-established hub there with about 300 daily departures, and

Southwest Airlines

(LUV) - Get Report

has said it will begin Dulles service this fall, although it hasn't specified a destination. Low-fare carrier Flyi briefly operated a Dulles hub until it shut down in January, a failed experiment in operating 50-seat airplanes at below-cost fares.

The New York-Washington market isn't exactly underserved. Nearly five dozen flights operate daily in each direction. Delta and

US Airways

(LCC)

each operate shuttles with 16 daily flights between La Guardia and National.

American flies six flights a day from LaGuardia to National and four a day from Kennedy to National, using 44-seat and 37-seat regional jets. From Newark,

Continental

(CAL) - Get Report

operates eight flights a day to National and six to Dulles.

Delta and JetBlue have different reasons for entering the Kennedy-Dulles market, and both face their own challenges.

"The purpose of our service is to feed the international operation at Kennedy," says Delta spokeswoman Gina Laughlin. "For people who want to travel to places like Kiev, this provides an opportunity to get there with just one ticket."

Delta is trying to boost revenue and emerge from bankruptcy protection by increasing its international revenue to 50% of its total in three years, up from 20% a year ago and an expected 35% at the end of this year.

To reach its goal, Delta is using two vastly different platforms. One is Atlanta, where it already operates the world's biggest hub with about 1,000 flights a day and plentiful connections. The other is Kennedy, which serves the country's biggest international travel market, New York, but has limited feed traffic.

The 37-seaters operated by

Mesa Air Group

(MESA) - Get Report

can certainly deliver connecting passengers, although it's hard to imagine that they would win any points in a comfort battle with JetBlue's newer, roomier, leather-seated, live TV-equipped 100-seat regional jets.

But JetBlue has to hope there are enough passengers who want to fly between two remote airports. JetBlue, although it has a Kennedy hub, connects only about 10% of its passengers. Its intent is to stimulate point-to-point demand with low fares.

"Every day, one thousand fewer people fly each way between New York and Washington, D.C., today compared to summer 2001," said CEO David Neeleman in a prepared statement. "We think there's a good reason why: fares are too high, which makes taking the train or driving a viable alternative."

JetBlue says its one-way fares will range between $50 and $145, or 20% to 80% lower than existing fares.

The new service may take some passengers from the shuttles, and may force some limited fare adjustments. Still, the shuttles, which have competed with Amtrak for years, offer obvious benefits for business fliers, including hourly service.

"We're confident that Reagan National and LaGuardia are the preferred airports in Washington and New York," says US Airways spokesman Phil Gee. "We will compete with anyone who wants to add new routes in our backyard."

Virginia-based aviation consultant Darryl Jenkins doubts the shuttles will suffer much impact from Dulles service. "It's quite a hike to Dulles," he says. "The traffic is very severe, Metro doesn't go there, and it's a pretty expensive taxi ride from the city."

Consultant Mike Boyd says that despite a new subway line, Kennedy has similar problems, including a steep cab fare from Manhattan. But JetBlue has new regional jets arriving and needs new markets, and Boyd says the airline can take advantage of a loyal customer base.

"For JetBlue, the quality of their service is their No. 1 asset," he says. "JetBlue doesn't really have passengers -- they have groupies who follow the airline around like it's a rock band."