The portion of the Silver Line between its split from the Orange Line and Wiehle–Reston East station is in Fairfax County, Virginia and was constructed as Phase 1 of the Dulles Corridor Metrorail Project. Phase 2 expands the line another to Ashburn in Loudoun County, via Washington Dulles International Airport, adding six stations to the line. Construction of Phase 2 began in 2014; its opening is expected in early 2022. The $6.8 billion project is Metro's largest expansion by route mileage since its inception in 1976.