In a statement, the giant airplane maker said the new schedule reflects the previously announced need to reinforce an area within the side-of-body section of the aircraft, along with the addition of several weeks of schedule margin to reduce flight test and certification risk.

The 787 team working the side-of-body reinforcement has completed initial testing and is finalizing design details of new fittings that are expected to ensure full structural integrity of the joint.

"The design details and implementation plan are nearly complete, and the team is preparing airplanes for modification and testing," said Boeing chairman, president and chief executive officer Jim McNerney.

Boeing has postponed the 787's first flight for five times in past two years, citing parts shortages, defects, redesign work and problems with suppliers for disrupting development, although the company projects achieving a production rate of 10 airplanes per month in late 2013.

The endless delays of 787 did serious harm not only to the company's credibility, but also to its earnings as the costs and penalties climbed higher and higher.

Boeing pointed out that costs previously recorded for the first three flight-test airplanes will be reclassified from program inventory to research and development expense, resulting in an estimated non-cash pre-tax charge of 2.5 billion U.S. dollars, or 2.21 dollars per share for the third quarter.

Boeing will update its 2009 financial guidance in October when it reports third-quarter results.

Sparked by the new first flight schedule, Boeing stock soared 4.07 dollars, or 8.51 percent, to 51.89 at noon.