A Boeing Dreamliner took off from Paine Field for the final certification test of the new 787 battery system.

The jet successfully completed the test flight when it landed in Everett at 12:20 p.m. It took off just after 10:30 a.m. and was in the air for two hours.

The flight is the certification test for a new battery system. The test was to demonstrate that the new system performs as intended during normal and non-normal flight conditions, Boeing spokesman Marc Birtel said in a written statement.

The 787 Dreamliner has been grounded since mid-January because of smoldering batteries, including a fire on the ground in Boston. Boeing has designed what it says is a fix, including more heat insulation and a battery box designed so that any meltdown of the lithium-ion battery will vent the hot gases outside of the plane.

On March 12, the Federal Aviation Administration approved Boeing's plan to test the redesigned battery system, and Friday's flight test was the final part of that plan. The flight was to demonstrate the battery fix for the FAA.

The same plane, built for LOT Polish Airlines, flew on Monday in a pre-delivery check flight, where pilots did things like raise and lower the landing gear and ran backup systems.

The FAA will still need to approve the results and certify the battery system before airlines can fly 787s again. Fifty 787s owned by eight airlines have been grounded worldwide. Boeing has said it will install the battery fix on those planes first, and then on the 787s it has continued to build while the planes have been grounded.

The root cause of the battery problems still isn't known. Boeing executives have said that other airplane problems have been fixed without understanding exactly what caused them. The big question for Boeing in the weeks ahead will be whether the FAA agrees. The FAA has not laid out a timetable for a final decision about the fix.

The National Transportation Safety Board, which investigates aviation incidents but doesn't have enforcement power, plans a two-day hearing on the 787 incidents beginning April 23.

Boeing Co. shares had declined earlier in the day, but after the test was announced they were up by $1.11 at $86.06 in afternoon trading.

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