THE AUTHORITY that controls Dulles International and Reagan National airports has proved regrettably lax at governing itself. That failing has now led Ray LaHood, the U.S. transportation secretary, to appoint a federal watchdog to oversee it. The appointment comes at a critical moment, for unless confidence in the airports authority is restored, it could jeopardize completion of the most important infrastructure project in the Washington area, Metro’s $6.6 billion Silver Line extension to Dulles.

The Silver Line, whose construction and financing are being managed by the airports authority, is at a delicate juncture. To pay for the project, the authority is relying heavily on toll increases that will be levied on Dulles Toll Road commuters — far too heavily, in the view of many commuters and local officials. If it is to cushion the impact on those commuters and dampen political opposition, the authority needs several things: substantial federal transit loans on favorable terms; additional funding from Virginia, whose contributions to the project have been modest until now; and the confidence of bond rating agencies in New York, whose judgments will determine borrowing costs for the Silver Line.

The trouble is that all those things are imperiled by the steady drip of news about spendthrift habits, spotty procedures and inadequate controls at the airports authority — specifically involving its board of directors. Some of those revelations have been tawdry, particularly those involving some board members’ lavish travel expenses. Others suggest a cavalier attitude toward financial management, such as the board’s decision to make generous payments to an unsuccessful candidate for the authority’s top job and to a retiring board member.

The reports have prompted criticism of the agency, especially from Virginia officials, and, increasingly, calls for an overhaul in its governance. If the airports authority remains at the center of an intensifying political storm, odds are slim that it will secure federal financing on favorable terms or state aid that it deserves. The victims will be toll-road users, whose tolls will soar to pay for the Silver Line.

The watchdog appointed by Mr. LaHood is Kimberly Moore, a former Virginia state prosecutor who, as a lawyer for the Transportation Department for the last several years, has worked on ethics and procurement issues. She seems well qualified to push the authority to tighten policies and procedures on travel and contracting, for starters.

In particular, Ms. Moore could provide a blueprint to the authority to stanch problems involving hundreds of millions of dollars in under-the-radar contracts meted out with little oversight or regard for proper procedure, according to an interim report this spring by the Transportation Department’s inspector general. She might also provide a counterweight to what the inspector general found was the board’s inordinate fondness for secrecy and its wariness of transparency and financial disclosure.

Those would be good initial steps toward restoring confidence in the airports authority as it navigates construction and financing for the Silver Line’s completion. The real test will be whether the authority itself, which has too often turned a deaf ear toward suggestions for reform, finally decides to heed constructive advice.