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Boeing moved aggressively Wednesday to counter worries about the safety of the 787 Dreamliner, and airlines already flying the 787 rushed to offer their support for the new jet.

Addressing one of the more worrisome scenarios suggested by the battery fire on the ground Monday at Logan International Airport in Boston, a senior Boeing executive insisted that if a similar event were to happen in flight, smoke wouldn’t enter the passenger cabin.

The fire in the parked plane was discovered when a maintenance mechanic noticed smoke in the cabin.

“On the ground, in an unpowered airplane, we have really no ability to control where the smoke goes beyond the initial barriers that are in place,” 787 chief project engineer Mike Sinnett told journalists on a teleconference. “In the air, the pressurization of the cabin helps us a lot. It allows us to very easily … control the volume of air moving overboard.”

If smoke is detected in flight by a monitoring system in the electronics bay that houses the battery, the airflow and the smoke would be redirected outside, he said.

The fire at Logan broke out less than half an hour after the jet landed with 183 people aboard at the end of a 12-hour flight from Tokyo. In the wake of a wave of recent 787 electrical-system issues, the incident worried both the traveling public and Boeing investors.

Sinnett mounted a stout public defense of the Dreamliner’s safety Wednesday, adding a few details beyond those provided to The Seattle Times in an interview the day before.

Overall, Sinnett said, “I’m 100 percent convinced the airplane is safe to fly.”

Hans Weber, a respected technical authority in the aviation world and president of consulting firm Tecops International, concurred that the Dreamliner’s electrical-system design is safe.

Weber said industrial grade lithium-ion batteries have been in use for various applications including automotive batteries for some time. These are much higher quality than the mass-produced batteries used in laptops and cellphones.

He added that the venting of the electronics bay described by Sinnett “adds to my respect for the 787 design.”

Sinnett laid out a litany of protective measures, starting with four independent controls to prevent overcharging of the battery, which could cause a high-energy fire. A lesser battery fire is possible, but Sinnett said he’s confident that Boeing’s multiple safety measures ensure such a fire would be contained.

In the case of a fire while on the ground, Sinnett said, the electronics bay’s containment barriers would hold back smoke long enough to allow passengers to get out safely.

Besides the airplane’s design, quality control is a separate area of concern, especially at suppliers providing components of the system.

Four previous electrical system faults on in-service aircraft were traced back to a single batch of circuit boards “manufactured at one time by a sub-tier supplier,” Sinnett said.

Weber said that suggests lax oversight.

“The question is do they have adequate control of their production processes at their various suppliers,” he said.

Sinnett emphasized that those circuit-board problems produced faults that, though troublesome and expensive to the airline, posed “no safety issue whatever.”

Even airlines affected by recent incidents stepped up to support Boeing’s jet Wednesday.

A spokeswoman for JAL, on whose plane the fire occurred, said it does not intend to cancel any 787 orders.

Qatar Airways Chief Executive Akbar al Baker, frequently a sharp critic of both Airbus and Boeing, in an interview with Bloomberg News minimized the recent 787 incidents as “small teething problems.”

G. Prasada Rao, a spokesman for Air India, which received its sixth Dreamliner on Jan. 7, told Bloomberg its jets are “operating smoothly.”

Sinnett’s presentations and the surge of airline support evidently reassured investors. Boeing’s stock more than recovered all its losses from Tuesday, rising $2.63, or 3.5 percent, to close Wednesday at $76.76.

Dominic Gates: (206) 464-2963