A Boeing 787 from Seattle on Monday completed a test flight to see if a redesigned battery system works properly while the plane is in the air.

The test flight is an important step in Boeing’s plan to convince safety regulators to allow airlines to resume using the plane, which the company calls the Dreamliner.

Boeing filed a flight plan shortly before the plane took off from Paine Field near Seattle.

In a Twitter posting, the company said the flight “went according to plan” and that crews are now preparing for the battery certification flight test in the “coming days.”

Boeing Co.’s new 787s have been grounded since January, when a lithium-ion battery on one plane caught fire after it landed in Boston and the battery on another began smoking during a flight in Japan, forcing an emergency landing.

Boeing added insulation around battery cells and a steel casing on the outside to prevent fires. Company officials have said that they might never know the cause of the smoldering batteries, but they hope to get the planes back in the air within weeks, not months.

The National Transportation Safety Board and Japanese authorities are investigating the incidents.

The NTSB plans to hold a forum next month in Washington on the use of lithium-ion batteries in transportation. The agency said Monday that the event April 11 and 12 will focus on design and performance of the batteries and regulation of their manufacturing and use.

Monday’s test flight lasted two hours and nine minutes, Boeing said.

Boeing used a 787 that it built for LOT Polish Airlines.

Boeing spokesman Marc Birtel said the plane’s crew would test landing gear, electrical and backup systems, and “demonstrate that the new battery system performs as intended during flight conditions.”

Birtel said Boeing will analyze data from it and prepare to seek certification.

Boeing declined to provide access to the plane or its facilities before or after the flight.

The company makes the airplanes in Everett, Wash., and North Charleston.

Five of the jets were parked outside Boeing South Carolina final assembly plant on Monday.

The Post and Courier contributed to this report.