THE BOARD THAT runs the Washington area’s two main airports finally made a good call Wednesday. It reversed its previous, spendthrift decision to build an underground Metro station at Dulles International Airport, where an aboveground station would save hundreds of millions of dollars at no significant cost to passenger convenience.

In doing so, the board of the Metropolitan Washington Airports Authority, the construction manager for Metro’s Silver Line extension to Dulles airport and points west, demonstrated it is getting serious about completing the project in a cost-efficient, politically workable way. Dulles rail may just have been rescued from an untimely demise.

The board’s reversal came at the urging of U.S. Transportation Secretary Ray LaHood, who agreed to mediate what had become a bitter impasse between the airports authority and Virginia and local officials. The officials were concerned about the project’s spiraling price tag, which would be borne largely by users of the Dulles Toll Road.

To his credit, Mr. LaHood quickly grasped that success had little to do with the precise location of the Metro station at Dulles and everything to do with cost-cutting. He also understood that to get the Silver Line built, the perfect was the enemy of the good — and in any event, there was no perfect option on the table. Everyone involved, including the airports authority, accepted that building a Metro station directly under the main terminal at Dulles was unaffordable. The only question was how far away from the terminal the station should be.

The airports board accepted that a rational cost-benefit analysis favored the aboveground station, which will require passengers to spend an extra 2 or 3 minutes on a moving sidewalk but will save $404 million.

That is the most important chunk of savings in Mr. LaHood’s blueprint to get the second and final phase of the Silver Line built for about $2.8 billion — a major improvement on a project once pegged as high as $3.8 billion. However, it is not quite the end of the challenges facing Dulles rail.

Under the deal proposed by Mr. LaHood, the cost of building the Metro station at Route 28 — the station just east of the airport — is being shifted from the airports authority to Fairfax County. The estimated construction cost of that station, not counting a $53 million garage, is $80 million. That’s a significant and sudden burden to be asked to assume in the current economy, even for a county with Fairfax’s deep pockets.

Quite reasonably, Fairfax is asking for financing help from the federal government as well as from Virginia, and both have indicated they will come forward. They may also help with redesigning the station to attract private developers who may be interested in helping pay for the station as part of a project that might include new office, retail and residential space. Fairfax should not be expected to swallow the cost of the station whole.

Every publicly financed project must offer value and embrace efficiencies, to justify its expense, particularly a major one such as Dulles rail whose total cost will be in the $6 billion range. For a time, the airports authority seemed to have lost sight of its basic responsibility in that regard. Now, with a critical assist from Mr. LaHood, Dulles rail looks to be back on track.