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SEATTLE - Boeing said Wednesday it has extreme confidence in its 787 Dreamliner even as federal investigators try to determine the cause of a fire that has prompted new worries about the plane.

A top Boeing engineer said the company does not plan to change the lithium ion battery technology used in its 787 Dreamliners until investigators gather more information about what caused a fire on Monday in the battery compartment of a Japan Airlines plane parked at Boston's Logan International Airport.

Mike Sinnett, the chief engineer for Boeing's 787 program, also said the rate of problems experienced in the new planes is no higher than what Boeing saw in the 1990s with its 777 program.

We re not satisfied until our reliability and performance is 100-percent, Sinnett told reporters.

Sinnett briefed reporters Wednesday about the 787 battery system, noting that the FAA gave Boeing a waiver to use large, 32-volt lithium ion batteries on the plane. Boeing went with lithium ion batteries because of the advanced electrical system built into 787s, he said.

The battery that caught fire in the Boston incident was associated with the auxiliary power unit in the plane's tail.

Lithium ion batteries are a concern because each contains its own oxidizer -- making any fire that happens much harder to put out. In Monday's incident in Boston, a battery exploded ater firefighters finished putting out the flames, according to Logan airport fire officials.

Sinnett did not address Monday's incident, citing the ongoing investigation by the National Transportation Safety Baord. But he described the plane's safety features. To guard against explosion, each of the two batteries on board have four systems to prevent overcharging, he said. And in the case of a fire occurring in flight, the 787 is designed to vent any smoke outside. Keeping smoke out of the cabin when the plane is parked on the ground, however, is more difficult.

Investors rallied behind the company Wednesday. Boeing shares gained 3.2 percent to $76.47, after dropping 4.6 percent the two previous days.

The Dreamliner has had a rough stretch. Besides Monday's fire aboard an empty Japan Airlines plane in Boston, a separate JAL 787 experienced a fuel leak on Tuesday. And All Nippon Airways cancelled a domestic 787 flight in Japan Wednesday when a computer system indicated a problem with the plane's brakes. Last month, a United Airlines 787 flying from Houston to Newark, N.J., diverted to New Orleans because of an electrical problem with a power distribution panel.

Additional reporting by the Associated Press.

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