Escalating costs may present an unexpected obstacle to the scheduled spring 2008 start of construction on the 23–mile extension of Washington, DC's Metrorail system to Dulles International Airport. According to a new report by the U.S. Department of Transportation's inspector general, the cost of project's 11.6–mile first phase––currently estimated at $2.7 billion––has nearly doubled since December 2004. The rise threatens to push the public–private project beyond cost–effectiveness criteria necessary to receive $900 million in federal funding under the Federal Transit Administration's New Starts program.

The extension is a collaboration of the Commonwealth of Virginia, the Metropolitan Washington Airports Authority, and Dulles Transit Partners (DTP), which co–owned by Bechtel Infrastructure, Inc. and Washington Group International. The report speculates that the cost increase may be due in part to a lack of competition for the design/build contract, which was awarded under a Virginia law that permits negotiations with a single bidder for large–scale transportation projects. In addition to the FTA grant, the extension is to be funded by a $375–million loan, revenue from the adjacent Dulles Toll Road, and other local sources.