Investigators still don’t know what caused batteries on two Boeing Co. 787s to malfunction earlier this month, and the model remains grounded by the Federal Aviation Administration in the U.S. and by similar agencies overseas.

Meantime, local officials and analysts are pondering how long the investigation will take — and its cost.

Boeing’s cash flow is affected when it can’t deliver completed planes, and there could be other costs, such as reimbursements for airlines that had counted on the planes’ availability and modification of electrical systems on completed planes, should that be necessary.

Howard Rubel, a Jefferies &Co. analyst, suggested Boeing could take a $5 billion hit under a worst-case scenario. But Rubel only sees a 4 percent chance of that happening. The grounding will most likely cost Boeing $550 million, Rubel wrote in a report.

Doug Harned, a Sanford C. Bernstein &Co. analyst in New York, estimated Boeing’s expense at less than $350 million.

And a materials chemistry professor from MIT told Forbes that Boeing’s 787 could be grounded until 2014 if the company is forced to replace the 787’s lithium-ion battery with older, more typical battery technology.

Here in Washington, officials have expressed a greater level of faith in Boeing’s ability to return the 787 to the air. The main concern is a halt in airplane production, which could affect employees.

Gov. Jay Inslee believes the “most excellent engineers and machinists at Boeing” will resolve the problems with the 787.

“I have some degree of confidence we are going to do that and not end up in some … long-term shutdown situation,” Inslee said last week.

John Monroe, chief operating officer for Economic Alliance Snohomish County, doubts the FAA’s grounding of the 787 will have much impact on Snohomish County, where Boeing’s original 787 line is located, as long as the problem doesn’t drag out. The 787 is a small but important subset of the county’s aerospace industry, Monroe said last week. Aerospace employment makes up about 16.5 percent of county employment but 30.4 percent of wages, he said.

“We as a community need to be as supportive as we can,” Monroe said. “Our community takes great pride in the Boeing Co.’s accomplishments and when things do not go as planned, we as a community feel the hurt and pain as well.”

Once Boeing determines the cause of the 787’s problems, the company will act quickly, even if the solution requires a design change or changes to airplanes in production, said Monroe, a retired Boeing executive.

On Monday, Lori Gunter, a Boeing spokeswoman, confirmed that the company continues to build the 787 at a pace of five aircraft monthly, with no plan to slow production.

A few years ago, as Boeing struggled through Dreamliner development challenges, the company parked early-built 787s at Paine Field in Everett. Company employees have been gradually bringing those aircraft up to delivery specifications.

In 2012, Boeing reduced the number of aircraft parked on the flight line, including 787s and 747-8s, by about 40 percent from the previous year, Pat Shanahan, vice president of airplane programs at Boeing, said in an interview in December.

So far, the FAA grounding of Boeing 787s hasn’t affected operations at Paine Field in Everett, the site of Boeing’s big factory. But Dave Waggoner, the airport director, declined Monday to speculate about how many more parked 787s Paine Field could accommodate. Under the FAA order, the planes cannot even be flown for testing or to other airports for storage.

The 787 grounding comes as Boeing hopes not only to increase production on the Dreamliner to 10 monthly this year but also as the company plans to begin assembling the first 787-9. Boeing had been expected to detail the number of 787s it will deliver this year when the company reports its 2012 earnings Wednesday.

Initially, authorities in the U.S. and Japan were focused on the 787’s lithium-ion battery. Over the weekend, Japanese aviation officials, who are investigating the Jan. 16 emergency landing of an All Nippon Airways 787, said they’ve found no evidence that battery-maker GS Yuasa is to blame. Instead, they’re looking at the maker of the 787’s battery-monitoring system, Japan’s Kanto Aircraft Instrument Co.

On Sunday, officials for the U.S. National Transportation Safety Board ruled out the 787 battery’s charging unit as a culprit. They were to provide an update on the investigation Tuesday.

Bloomberg News contributed to this report.

Michelle Dunlop: 425-339-3454 or mdunlop@heraldnet.com.