Boeing has said the inaugural flight of its long-delayed 787 Dreamliner would take flight by the end of the year, and that it hoped to deliver the first plane for service in the last quarter of 2010, some two years behind its original schedule.

The Seattle-based aerospace giant also said that it would cost an additional $2.5bn to get the troubled aircraft airborne, after determining that some of its initial test-flight aircraft would not make it to market because of the extensive alterations needed.

Boeing chairman Jim McNerney said the extra time would enable the remaining work to be completed.

“This new schedule provides us the time needed to complete the remaining work necessary to put the 787’s game-changing capability in the hands of our customers,” he said.

“The design details and implementation plan are nearly complete, and the team is preparing airplanes for modification and testing,” he added.

The maiden flight had been set for June 30 but just days before Boeing said it had discovered a weakness in the body of the aircraft.

The 787 has so far cost $10 billion to develop and is seen as a bid by Boeing to regain its crown from Airbus as the world’s most innovative and successful builder of commercial airplanes.

The mid-sized plane is designed to fly long distances and use 20 percent less fuel than other similarly-sized aircraft. A large proportion of the fuselage and the wing are made from carbon composite materials, making it lighter and therefore more fuel-efficient. The jets will feature larger windows, higher humidity and higher air pressure to help offset jet lag.

Carriers have lined up to put in their orders. The 787 became Boeing’s fastest-selling model, with 865 orders placed (worth around $150 billion), over 60 of which have since been cancelled because of the delays and the deteriorating economic climate.

The initial delivery to All Nippon Airways is unlikely to take pace until 2011, rather than next March as Boeing had originally planned.

The Japanese airline has voiced its disappointment over the delays.

“We understand the need to make the best and safest aircraft possible and appreciate that delays due to engineering issues of the current nature must be solved in order to move forward and achieve this,” ANA said. “However, as launch customer and future operator of the 787, the length of this further delay is a source of great dismay, not to say frustration.”