It's unlikely the long-delayed Silver Line extension to Dulles International Airport is ready to operate until mid-2021, Metro's general manager said.

The long-delayed Silver Line extension to Dulles International Airport and Loudoun County will likely not be ready for riders until spring or summer 2021, Metro General Manager Paul Wiedefeld said Wednesday.

While the Metropolitan Washington Airports Authority is responsible for construction of the line, the six new stations and 11.4 miles of track will be owned and operated by Metro after construction is substantially complete.

“We’re waiting for them [MWAA] to come back to us on a date. My best guess, it would be spring of next year,” Wiedefeld told a D.C. Council committee.

That appears to build in even more delays than the latest available estimates from the Airports Authority’s construction contractors.

Metro has scaled back hiring efforts for the extra people who will be needed to operate the line. The process was expected to significantly ramp up this winter.

Metro aims to time the most significant hiring process to begin about 9-to-12 months before the trains from Wiehle-Reston East to Ashburn begin to carry riders.

“As we have always said, WMATA will set the date to begin passenger service,” Airports Authority project spokeswoman Marcia McAllister said. “The Airports Authority is moving forward and working with our contractors and with WMATA to get this project completed.”

The authority is optimistic things are moving in the right direction, even if getting there may take hard work, good luck and good weather.

“We believe we’re making good progress,” McAllister said.

Currently, those involved in the project are awaiting a report from Metro’s Office of Inspector General on some of the significant problems with concrete station framing panels.

The Airports Authority believes the issues have been resolved and the panels, with once-a-decade sealant and other testing promises, funding and warranty, will meet a 100-year life span requirement.

Metro officials are not so sure.

If the panels do end up remaining in place, the biggest schedule issue causing months of delays appears to be automatic train control software certification concerns.

According to an Airports Authority update Wednesday, there is still no schedule or agreed upon scope of work to address problems with software safety documentation, so it is unclear when the testing and tie-in work to the existing line can happen.

The work is expected to take about three months of consecutive weekend closures of Wiehle-Reston East, which had been scheduled to end by March under original plans.

Other issues now being addressed include:

installation of windscreens at the Dulles station

fixes for at least 17, and up to 108, insulated rail joints

fixes for switch construction issues

Follow-up testing has confirmed previous concerns that concrete rail ties could have had problems were unfounded, and instead identified faulty installation as the cause of some issues.

Those issues are now being fixed.

Metro and the Airports Authority are still finalizing plans to fix problems with the rock ballast that supports the tracks in the rail yard, after 30 out of 90 sampled areas were found to have problems.

The Washington Metrorail Safety Commission is also monitoring Metro’s decision making and training ahead of the line’s opening.