Maine probably dodged a bullet – no, make that a cruise missile – earlier this year when the Pentagon dropped plans to switch all DD(X) destroyer production to one shipyard.

The ships are currently made at BIW in Bath and Ingalls in Pascagoula, Miss. The Navy argues, rather persuasively, that concentrating the work in one shipyard would save money. Ingalls, meanwhile, would have a variety of advantages in a bidding war. It’s a much bigger yard, so it can spread administrative costs over more projects and it has a better deep-water port.

But Ingalls has another huge advantage: Its average labor costs are $3 per hour less than BIW’s.

That’s a big difference on a project as large and labor-intensive as building a modern battleship. It is not, of course, insurmountable as long as BIW’s processes and workers are that much more efficient and productive.

Recently, BIW announced plans to replace 27 union custodial workers with nonunion help from out of state. That move, of course, has drawn fierce opposition from the shipyard’s unions.

About 900 workers rallied outside the shipyard Thursday against the change, and another rally is scheduled for this week. “Morally and ethically, this is absurd,” said Mike Keenan, president of the shipyard’s biggest union. “These are the folks who have bled and sweated for this company.”

The union plans to fight the cuts, saying they violate its contract.

That may be so, but the union also needs to honestly face the dire reality of this situation.

The Navy clearly left the door open to revisiting its consolidation idea. There is little doubt that this threat will return, and the yard cannot always count on political pressure to keep the federal work flowing.

There is only one way to guarantee that the work will remain here: BIW must be able to establish that it can build boats faster, better and cheaper than Ingalls.

The best way to do that is for the union and management to work together to increase productivity and cut costs. That will require give-and-take; the union will have to carefully pick its battles.

Is it worth going to the mat for 27 custodial jobs? That’s a decision for the union members and leadership to make.

They must do so knowing, however, that if some changes and sacrifices aren’t made, all of this work may one day disappear.