Boeing won permission on Thursday for test flights of its 787 as it tries to fix battery problems that have kept the plane grounded.
The Federal Aviation Administration said the test flights will have restrictions, including pre-flight testing and inspections, and in-flight monitoring. The tests are limited to airspace over unpopulated areas.
Boeing said the tests will begin "soon" on one of the six airplanes it used for testing before the 787 was certified by the FAA in late 2011. It said the batteries will get a pre-flight inspection, and battery-related status messages will be monitored.
The plane, labeled ZA005, was seen on the ground at Boeing Field near Seattle with stairs leading to the two cargo doors near where the two batteries are housed, KING 5 TV reported on Tuesday.
Boeing said that flying the plane will allow it to test the in-flight performance of its batteries and generate data to help the investigations.
"The company has marshaled an extensive team of hundreds of experts and they are working around the clock focused on resolving the 787 battery issue and returning the 787 fleet to full flight status," Boeing said Thursday. It didn't say how many test flights are planned.
The planes still can't be used for passenger flights until the FAA is satisfied that the battery problem is fixed. The grounding order issued on Jan. 16 meant that Boeing even needed FAA permission to fly an empty 787 from Texas to Washington state on Thursday after it had been painted.
Each 787 has two lithium-ion batteries. One of them caught fire on a 787 after it landed in Boston on Jan. 7. Smoldering in another battery prompted an emergency landing in Japan on Jan. 16, leading to the FAA's order grounding the planes later the same day. The National Transportation Safety Board said Thursday that the Boston fire was sparked by a short-circuit inside one cell of the battery, but the cause of the short-circuit isn't known yet.