Boeing was forced to defend the safety of its 787 Dreamliner airplane Wednesday after three incidents in three days, saying it had “extreme confidence” in the innovative design and technology used in the plane.

The 787 has been in operation for 15 months, and Boeing has so far delivered 50 airplanes to eight airlines, including All Nippon Airways, Japan Airlines and United Airlines. Since then, a small number of 787s have had small electrical fires, fuel leaks or other problems, prompting a safety advisory from federal regulators.

This week, the National Transportation Safety Board opened a formal investigation after an electrical fire broke out in a lithium-ion battery pack used to power the auxiliary unit in a 787 operated by Japan Airlines that was parked at Logan International Airport in Boston. The fire occurred on the ground after the passengers and crew had gotten off.

On Tuesday, another of the airline’s 787s, also in Boston, was delayed for nearly four hours after a fuel leak. And Wednesday, All Nippon canceled a domestic flight after a computer on board erroneously showed problems with the plane’s brakes. These problems followed an earlier incident, in December, when a United Airlines 787 was forced to divert after one of its six electric generators failed in midflight.

Mike Sinnett, the 787’s chief project engineer, said Wednesday that the program suffered from no more problems than other new planes, like Boeing’s 777 when it was introduced in the mid-1990s.

The 787’s operational reliability – a measure of how often it leaves the gate on time without a mechanical problem – is in the high 90 percent, he said, a rate similar to the 777 at the same time in its production life.

“This is par for the course for any new airplane program,” Sinnett said in a conference call with reporters. “We have a responsibility and obligation to help assure people about the integrity and the robustness of the design.”

Asked whether the plane was safe, he responded: “Absolutely, I am 100 percent convinced the airplane is safe to fly. I fly on it myself all the time.”

He said the plane had a large number of redundant systems, meaning that if one or more failed, the plane could still fly and land safely. For instance, he said, testing had demonstrated the 787 could fly for more than 5-1/2 hours with just one of its six electrical generators functioning.

But questions remain about the high-profile jet, which has a lot riding on it both for Boeing and its airline customers. According to a story on The (Charleston) Post and Courier website, the company is ramping up plans to double production of the jet at its Everett, Wash., and North Charleston plants this year to help fill an 800-order backlog.

The 787 packs a lot more technology than traditional airplanes. It makes extensive use of lightweight carbon composites, has more fuel-efficient engines and relies mostly on electrical systems instead of mechanical ones to operate hydraulic pumps, wing de-icing systems, cabin pressurization and other systems. It also has electric brakes instead of hydraulically operated ones.

Instead of drawing air from the engines to operate these systems, the 787’s novel architecture eliminates most pneumatic systems and replaces them with electric ones. This increases the fuel efficiency of the airplane by 2 to 3 percent at cruising altitude, according to Boeing.

Randy Tinseth, Boeing’s head of marketing, said in a statement Tuesday that the 787 had logged more than 18,000 flight cycles and flown more than 50,000 hours.

“We have complete confidence in the 787 and vow to take care of any issues our customers are experiencing – day or night,” he said.

Investors rallied behind the company Wednesday. Boeing shares gained 3.2 percent to $76.47, after dropping 4.6 percent the two previous days. Associated Press and The (Charleston) Post and Courier contributed.