As Metro’s board of directors considers the details of operating the new rail extension to Loudoun County, it’s beginning to question the location of the stop at Dulles International Airport and what it will cost to manage 11 additional stations and 23 miles of track.

There are no easy answers.

Metro General Manager Richard Sarles said at a Thursday committee meeting of Metro’s board that staff will calculate estimates of what it will cost to operate the first phase of the Dulles rail line. Metro is also reviewing how many rail cars the transit agency will need on the new line and elsewhere in the system, determining final names for new stations and considering changes to Metro’s 35-year-old system map to reflect the growth.

Metro will operate the Silver Line to Loudoun. The Metropolitan Washington Airports Authority, which runs Dulles and Reagan National airports, is overseeing construction.

The Silver Line extension includes 11 new stations, with five in the first phase, scheduled to open in 2013, and six in the second phase, which is targeted for completion by 2016.

The second phase of the Dulles extension has come under scrutiny because of a debate between the airports authority and regional leaders over whether the station at Dulles should be closer to the main terminal and underground, at a higher cost, or farther away and aboveground.

Federal Transit Administration chief Peter M. Rogoff made suggestions to the stakeholders in the Dulles project of how to cut costs for the second phase of the project, which is now estimated to cost $3.5 billion. Federal transportation officials hope to get the cost closer to the original estimate of $2.5 billion. Transportation Secretary Ray LaHood has been mediating negotiations.

The federal suggestions for savings, detailed in a July 3 white paper, include: ordering fewer of the new 7000 series rail cars for the Dulles line; building a smaller rail yard and shop facilities; reducing the size of canopies; using steel structures instead of concrete; and using stamped concrete floors in stations instead of tiles.

“These are things we can live with,” Sarles said Thursday.

However, Sarles said one idea broached by Rogoff — reducing the number of power substations — is a concern. A reduction could cause a potential slowdown in restarting trains on the Silver Line and recovering the system if they had to stop because of a problem.

Rogoff appeared before the Metro board Thursday and answered questions about the proposed cuts. Board member Tommy Wells asked Rogoff about the best location for a rail station at Dulles. Rogoff answered with caveats.

“A lot of that comes down to who you envision as the principal passengers of the airport station,” Rogoff said. The Dulles line, he noted, will serve “the entire region of Fairfax and out to Loudoun,” not just the airport. Most of those using the Dulles station will be airport workers, not travelers, he said.

“Certainly for airport passengers, the closer you are to the terminal the more convenient it is,” he said. But, he noted, “our experience nationally is that the majority of users of rail transit stations at airports are not airport passengers carrying luggage.”

Sarles did not take a position on the location of the station.

“That’s a good question that’s being discussed by stakeholders, and they’ll come to a conclusion,” he said.

A board committee also decided to implement a policy to give the stations a shorter primary name and a longer secondary name for the remake of the Metro map. The full board still must approve that decision.