Boeing's new 787 Dreamliner finally took to the air on Tuesday, more than two years later than originally planned.

The plane's long-anticipated maiden flight was a milestone for the development of the aircraft seen as key to the U.S. aerospace heavyweight's future.

Braving the morning cold, a crowd of about 12,000 people, most of them Boeing employees, watched the jet take off at Paine Field Airport in Everett, a city about 40 kilometers north of Seattle, Washington.

After accomplishing its three-hour flight, which was trimmed from five hours due to bad weather, the Dreamliner landed at Seattle's King County International Airport, also known as Boeing Field.

During the flight, the two pilots -- Mike Carriker and Randy Neville -- tested the airplane's systems and structure while onboard equipment recorded and transmitted real-time data to a test team on the ground.

The first flight was "a very important milestone" in the development of the Dreamliner, Russ Young, Boeing's spokesperson, told Xinhua. "An airplane is designed to fly, so the first time you fly it is a great moment."

The 330-seat 787 will consume up to 20 percent less fuel for long-haul routes than today's similarly sized airplanes, Boeing said.

The plane was also dubbed the "green" passenger jet by Chicago-based Boeing because as much as 50 percent of the primary structure on the jet is made of composite materials, such as carbon fiber-reinforced resin.

Boeing says the 787 will be more efficient, quieter and have lower emissions than other airplanes. The midsize plane also will have wider seats and ailes, and larger windows.

Depending on its configuration, the plane will hold as many as 330 passengers.

Launched in April 2004, the 787 program has been plagued by repeated delays with the first flight postponed five times in the past two years.

"We have run into some delays. Those are disappointing. But it's the nature of our business, we have got to get the airplane right," said Young.

Finally getting the 787 off the ground was a relief for Boeing, which is hanging high hopes on the plane in regard to competition with its European rival Airbus.

Young said that Tuesday's first test flight was just one of the major milestones in a very long process of designing, testing, building and flying.

"There is lot to be done before we have it delivered," Young said.

According to Boeing, the 787 has already topped the list of the "fastest-selling all-new jetliner in aviation history" with 840 orders from 55 customers around the world.

The success of the maiden flight entitles Boeing to fast-track its orders since production problems pushed back delivery of the first plane to Japanese carrier All Nippon Airways to late 2010.

Until now, delays in the program were to blame for a 1.6-billion-dollar loss in the third quarter. Boeing also slashed this year's earnings guidance by more than a third.