EVERETT, Wash. — Boeing's new 787 jetliner finally got airborne yesterday, the long-delayed inaugural flight of the world's first commercial plane mostly constructed from lightweight composite materials.

The sleek jet lifted off from Everett's Paine Field on a flight over Washington state, beginning an extensive testing program needed to obtain Federal Aviation Administration certification.

"It's very historical. I can't think of a thing about it that I'm not impressed with," said Joe Bierce, a flight instructor for Delta Connection in Jacksonville, Fla., who was among the 25,000 people who gathered to watch the takeoff.

The two-member crew performed a variety of basic system checks, including testing the landing gear and the flaps, before landing at Seattle's Boeing Field about three hours later. Deteriorating weather brought the plane back to earth about an hour earlier than planned.

"The airplane responded just as we expected," said Randy Neville, one of the two pilots. "It was a joy to fly."

The plane is the first of six 787s Boeing will use in the nine-month flight-test program that will subject the planes to conditions well beyond those found in normal airline service, including temperature extremes, flying on one engine and slamming on the brakes at takeoff speed.

Chicago-based Boeing, which has orders for 840 of the jets, plans to make the first delivery to Japan's All Nippon Airways late next year.

The 787 is a radical departure in aircraft design. Where other passenger jets are made mostly from aluminum and titanium, nearly all of the 787's fuselage and wings are made of lightweight composite materials such as carbon fiber, accounting for about 50 percent of the aircraft by weight.

Those materials have long been used on individual parts such as rudders, and on military planes, but the 787 is the most ambitious use of the technology aboard a passenger plane.

Boeing says the aircraft will be quieter, produce lower emissions and use 20 percent less fuel than comparable planes, while giving passengers a more comfortable cabin with better air quality and larger windows.

Officials cut the flight a little short after rain reduced visibility at Boeing Field and the aircraft ran into poor weather off the coast.

The 787 remains Boeing's best-selling new plane to date, though some airlines have been forced to cancel or postpone purchase plans because of the weak global economy.

The version being tested will be able to fly up to 250 passengers about 9,000 miles. A stretch version will be capable of carrying 290 passengers and a short-range model up to 330.