The test flight was an important step in Boeing's plan to convince safety regulators to allow airlines to resume using the plane. Boeing used a 787 that it built for LOT Polish Airlines.
After takeoff at 12:11 p.m., the plane headed west to Neah Bay, then south along the Washington and Oregon coastline to Newport, Ore., where it reversed course. The Dreamliner crossed the Olympic Peninsula diagonally, then veered west again to the Pacific Ocean, returning to Paine Field at about 2:20 p.m.
Boeing Co. 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.
In redesigning the system, 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.
The National Transportation Safety Board and Japanese authorities are investigating the incidents.
In announcing the test flight, Boeing said in a statement that it would be "a normal Boeing production check flight intended to validate that all systems function as designed. During a functional check flight, crews cycle the landing gear and operate all the backup systems, in addition to performing electrical system checks from the flight profile. Across airplane programs, more than 600 functional check flights were completed in 2012.
"Following the completion of the functional check flight, we will analyze the data from the flight and prepare for certification ground and flight demonstration in the coming days," Boeing said.
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 11-12 will focus on design and performance of the batteries and regulation of their manufacturing and use.