THERE WERE two significant pieces of news last month about Metro’s Silver Line extension to Dulles International Airport, one of the nation’s biggest infrastructure projects, and together they could give Northern Virginia commuters whiplash.

First came the good news: The project’s $2.7 billion second phase — 12 miles of rail running from Reston to the airport and into Loudoun County — is likely to receive almost $1.9 billion in federal loans on highly favorable terms, a critical component of the hoped-for financing for a project that broke ground last year.

Then came the bad news: Completion of the project’s $2.9 billion first phase, 11 miles of rail from East Falls Church to Reston, would be delayed. Again.

To refresh the memory: Back in 2006, when the authority that runs Reagan National and Dulles airports took control of the project from the state of Virginia, the Silver Line’s first phase was expected to be completed in 2012 and the second leg in 2015 — all at a combined cost of $4 billion. Countless delays and cost increases later, officials are hoping the first phase is ready for passengers by early summer and the second phase by 2018 — all at a combined cost of $5.6 billion.

It’s almost inevitable that the time and cost goalposts will move in massive construction projects like the Silver Line. Still, it remains the case that from the beginning, the airports authority was an ill-suited overseer for an undertaking of these dimensions, despite its claims to expertise for having managed the construction of the four-mile Dulles airport train system connecting the main terminal with concourses. At the time, the authority’s real selling point was its plausible assertions that it could get the job done with relative immunity from political meddling — mainly by raising tolls on the Dulles Toll Road, which it controls.

The latest news on the Silver Line is dreary. State inspectors have ordered that hundreds of public-address speakers, which don’t meet fire code, be torn out and replaced at the five new stations of the first phase. A communications cable must also be upgraded. Those problems follow an earlier software glitch in a critical safety system, which delayed things for months. The grumbling over delays now directed at the state inspectors has supplanted earlier grumbling aimed at the airports authority board, its staff and the general contractors, a consortium led by the construction giant Bechtel Corp. It is, as board member Thomas M. Davis III aptly said, a soap opera.

Like all soap operas, this one will end — with passengers boarding Silver Line trains no later than June, we hope. That’s months later than officials had expected even a year ago, and it will cost Metro millions of dollars in lost revenue.

Still, it will be worth it if the system, once Metro takes control of it from the airports authority, is safe and reliable — and if the new contractors for the second project’s phase, a joint venture of Clark Construction and Kiewit Infrastructure South, take lessons from the missteps of the first.