SEATTLE (AP) -- A key section of a Boeing Co. 787 jetliner was damaged during assembly at a plant in South Carolina, raising the potential for new delays in getting the new aircraft off the ground.

The fuselage section for the company's fourth 787 on the assembly line was scheduled to arrive in Everett, Wash. by the end of June.

But an employee of Boeing partner Alenia North America "did not follow the documented work process, damaging the fuselage, Boeing spokeswoman Lori Gunter said Tuesday.

Gunter said the damage to airplane No. 4 will not affect the 787's first flight, currently set for the fourth quarter of this year, but she said Boeing was still assessing whether the overall flight test plan would need to be altered. That, in turn, could push back the delivery of the first finished plane to All Nippon Airways, now expected in the third quarter of 2009.

Airplane No. 4 is slated to begin its life as one of six test planes used to check everything from how the 787 handles at different altitudes and in different climates to how noisy it is in the cabin.

Some of plane No. 4's parts made it to Everett on time, but Gunter said that when Boeing learned of the damage to the midbody, it also asked manufacturer Spirit AeroSystems to delay delivery of the plane's nose.

Gunter would not give detailed information about the damage, but Flight International magazine's Flightblogger Web site reported Monday that the plane's composite materials were wrecked when an employee tried to assemble pieces using the wrong fasteners. The Seattle Times relayed the details on Tuesday.

The 787 is Boeing's first newly designed jet since airlines started flying the 777 in 1995, and it will be the world's first large commercial airplane made mostly of carbon-fiber composites, which are lighter and more durable than aluminum.

The new jetliner's first flight has been repeatedly delayed by parts shortages and early assembly snags, as Boeing worked out the kinks in a new system that relies much more heavily on work done by outside companies.

Boeing bought out Vought Aircraft Industries' stake in the Charleston, S.C. plant in a bid to curb production delays, and now jointly operates it with Alenia.