The first phase of Metro's silver Line was expected to open this December, but officials now say that launch date will be pushed back to January.
Sam Carnaggio, director of the Dulles Corridor Project at the Metropolitan Washington Airports Authority, said construction work is 94 percent complete.
The contractor is expected to finish by the end of September, so the project should be turned over to Metro by October, Carnaggio told WTOP-FM.
Metro will then need at least 90 days to independently test the trains and tracks and hire staff, he said.
Work on the second phase, which will extend Metrorail into Loudoun County past Dulles Airport, is expected to begin in July and be complete in five years.