Boeing Co. said Wednesday that it will delay delivery of its fast selling 787 Dreamliner jet by six months because of continued challenges in the plane's assembly, including parts scarcity.

The Chicago-based firm said the new schedule takes into account unexpected problems that could slow down ground and flight tests. Among the impacted customers will be Japan's All Nippon Airways Co. which had been scheduled to receive the first plane.

The company said 15 of the 787's 50 customers will be affected by the delay. The first deliveries will take place in November or December. The first test flight is expected to take place by the end of March 2008, rather than then end of this year.

We deeply regret the impact these delays will have on our customers, and we are committed to working with them to minimize any disruption to their plans, Scott Carson, chief executive of Boeing's commercial airplanes unit, said in a statement.

The company said the delay would not be material to earnings, keeping its current 2007 and 2008 forecasts. The company has already taken about $120 billion in orders of the plane, its most successful debut for a plane.

The 787 has been lauded for its innovative approach to design which integrates lighter materials, energy efficiency through new engines and its advancements in assembly processes.