The time for a workable Plan B is the moment when Plan A is put in serious doubt. That moment came for Honolulu’s rail project when its cost overruns compelled the development of a “recovery plan” for the Federal Transit Administration, a blueprint to finance the completion of the 20-mile project’s final 4-mile stretch.

The pandemic and other complications pushed the deadline for that required plan until the end of 2021, but the project shortfall now has ballooned to $3.68 billion. And that means the basic contours of the project may need amendment, what some members of the Honolulu Authority for Rapid Transportation describe as “Plan C.”

Could the project stop short of its long-planned Ala Moana Center terminus, which remains the ideal? Some have suggested a Middle Street end point, but critics rightly assert that extending at least to downtown is needed to make the system at all useful.

It’s a debate that has been stalled but really can be delayed no longer. Exploring fiscally viable alternatives that can produce a workable rail system should now be the focus of HART and city officials. This work will help inform discussions Mayor Rick Blangiardi and HART executives plan to have with the FTA in the coming months.

The project’s current fiscal crisis also is factoring into decisions to fill a vacancy on the HART board. The Honolulu City Council nominated Anthony Aalto, a filmmaker who, critics say, tilts toward pro-rail interests. He would replace Joe Uno, a construction cost estimator whose term just ended.

But at a Wednesday press conference, Council members Augie Tulba and Heidi Tsuneyoshi announced a proposal to reappoint Uno instead. Tulba cited Uno’s expertise in “safety, as well as the financing of the rail.” Tsuneyoshi said the nomination resolution would boost the required qualifications.

“What’s really driving me right now is the fact that we don’t have a way to pay for the rest of the way,” Uno rightly said.

Ultimately, the Council will need to assess what qualities in a board member would best serve the HART mission, both near- and long-term.

In an op-ed the Honolulu Star-Advertiser published July 19, Aalto was clear on the project’s priority aims to provide traffic relief and enable affordable housing development. That perspective also is important.

Whoever is at the helm, it’s essential that the board increase its transparency to bolster the public trust, which has been under severe strain.

There is a lot of ground to cover in the coming weeks, especially considering the deep hole into which Honolulu has fallen. This conclusion can be drawn from comments by a retired FTA official.

Ron Fisher, formerly director of the FTA Office of Project Planning in Washington, D.C., told Honolulu Star-Advertiser writer Dan Nakaso that the financial deficit is “unimaginable,” compared with anything he’s seen in 30 years.

And he doubts that HART can persuade current FTA officials to make up the shortfall, which itself may not be reliable.

“It would be highly unusual for FTA to say, ‘We’re going to reward you with additional money for a project that seems to be incurring incredible cost overruns,” Fisher said in the interview, published Tuesday.

So this is a signal — a strong one — that HART will need to think outside the box. A list of 27 options — ranging from changing plans for rail stops to shifting the guideway or moving it to another corridor altogether — has been floated.

As Fisher correctly notes, though, there should be a “data-driven” analysis of all alternatives. HART must decide for which ones there are realistic pathways, while still yielding a rail system Oahu residents will want to use.