Officials at the Metropolitan Washington Airports Authority said Wednesday that “substantial completion” of the first phase of the Silver Line rail extension could be delayed by at least eight weeks.

“There’s a real question now on when it will be complete,” MWAA CEO Jack Potter told members of the board’s Dulles Corridor Committee during a briefing on the rail project.

The announcement means that passenger service on the rail line is unlikely to begin in December and casts doubt on whether it could start in January as well.