WOULD YOU PAY $330 million to shave 2 minutes and 40 seconds off your trip to the airport? Or would you pocket that money and put it to better use?

The authority that runs Washington’s two major airports thinks $330 million is a fair price to pay for an underground Metro station at Dulles International Airport — rather than an aboveground one 500 feet farther from the terminal — that would save an airport-bound passenger exactly 2 minutes and 40 seconds at a normal walking pace on an existing underground moving walkway.

That’s not just a staggeringly reckless waste of public money. It’s also a decision that threatens to kill the single most important public transit project in the national capital region — the Silver Line extension of Metrorail to Dulles — by driving its cost to $3.5 billion from $3.2 billion.

A chorus of voices, including business groups, leading transit experts and government officials at all levels, has raised the alarm in opposition to the airports authority’s profligacy. The authority needs to come to its senses, and to a better decision, quickly.

The stroll on the moving sidewalk from the proposed underground station would take about 1 minute and 59 seconds. The stroll from the aboveground station, which would be located in front of the existing garage, would take about 4 minutes and 39 seconds. So the airports authority is willing to spend other people’s money to the tune of $2.06 million per second of not-very-much saved time.

Sharon Bulova, chairman of the Fairfax County Board of Supervisors, led a gaggle of reporters along the existing underground walkway from the garage to the terminal at Dulles the other day to make the point: Tens of thousands of people use it already every month. It works. It’s air-conditioned. It’s efficient. It’s easy. If you don’t feel like walking, you can stand.

In voting 9 to 4 this month to build a tunnel and underground Metro station, the airports board ignored the strenuous opposition of Fairfax and Loudoun counties, which together would pay about 20 percent of the Silver Line extension to Dulles and points west; of Republican Rep. Frank Wolf, in whose district the project would be built; of the Virginia Chamber of Commerce; and of Dulles Toll Road commuters who would pick up three-quarters of the tab through toll payments. Moreover, the authority disregarded the recommendation of its own professional staff, in whose view the aboveground option made more sense.

Since that decision, members of the board’s majority have offered an array of hollow arguments to justify their decision.

They say the aboveground option would interfere with the view of the terminal’s architectural grandeur. Nonsense. The aerial station would be located in front of the existing garage. And while the aboveground Metrorail line would cut across the airport access road, it would also afford arriving and departing train passengers a dramatic view of architect Eero Saarinen’s graceful masterpiece.

The authority argues that arriving passengers would be put off by having to wait in extremes of heat or cold for a Metro train to arrive at an aboveground station. But why couldn’t the aboveground station platform be enclosed and climate-controlled — for a good deal less money than $330 million?

The overarching theme of the majority’s stance is that the location of the Metro station at Dulles is a critical long-term decision and that the region has to get it right lest the airport suffer dire economic consequences. As a cautionary tale, some members of the authority have cited the inconvenience suffered by Metrorail passengers at Reagan National before that airport’s new terminal opened, closer to the station, in 1997.

But this, too, is an empty argument. Before the new terminal was built at National, Metrorail passengers were forced to walk across a street, with no protection from traffic or the elements and no moving walkway. It was a trudge and a hassle — and bore no relation to the smooth underground moving walkway already operating at Dulles. What’s more, no one has offered a shred of evidence that any long-term economic harm would befall Dulles as a result of spending an extra 2 minutes and 40 seconds on an underground moving walkway.

Yes, there are concerns about the aboveground station, and it is important they be addressed. Accommodations would have to be made for the convenience of passengers arriving with heavy luggage, so that luggage could either be placed easily on the underground walkway or be checked and conveyed from the station to the terminal. Engineers designing the aboveground station would need to prioritize long-term maintenance, so that elevators conveying passengers between the platform and the moving walkway are reliable, quick and simple to use.

The fight over the Metro station at Dulles has reached a dangerous impasse; as a result of the authority’s misguided stance, there is a real peril the project could collapse. Loudoun County officials have called the decision an “outrage.” If the county quits the deal, that would probably rob the Silver Line of thousands of daily commuters and play havoc with Metro’s financial projections for the second phase of the extension.

Fairfax is similarly upset. There is a growing risk of litigation. If that happens, it could imperil the county’s dedicated tax district, whose purpose is to cover 16 percent of the Silver Line’s cost. Unless Fairfax commits unequivocally to the project by the end of this year, the tax district automatically starts a 24-month countdown to its own dissolution. If the tax district disappears, so does the second phase of the Silver Line — and the prospect of a modern transit link with the region’s premier international gateway airport.