Deliveries of US planemaker Boeing's new 787 Dreamliner aircraft will fall six months behind schedule, the company has announced.
The delay - to late November or December 2008 - was caused by manufacturing problems, Boeing said.
Half the materials used to build the Dreamliner are carbon fibre composites, making the process more complex.
The A380 superjumbo, the flagship of Boeing's arch-rival Airbus, has itself been hit by repeated delays.
The news had an impact on Boeing's share price, which fell 2.7% on Wall Street.
This was despite Boeing saying that the setback would not have a substantially negative impact on its balance sheet.
The firm added it "deeply regretted" the delay - a result of problems with spare parts, software and systems integration - and would work with its customers to minimize disruption to them.
"We are disappointed over the schedule changes that we are announcing," said Jim McNerney, the firm's president and chief executive.
"Notwithstanding the challenges that we are experiencing in bringing forward this game-changing product, we remain confident in the design of the 787 and in the fundamental innovation and technologies that underpin it."
The Dreamliner's maiden flight is now expected to be some time next Spring.
Boeing's customers reacted cautiously to the news with Japan's All Nippon Airways, which will take delivery of the first plane, saying it would not have a "huge impact" on its business.
Qantas said it had been assured that the first of 15 aircraft due for delivery from August 2008 would arrive within six months of the original date.
The Dreamliner, Boeing's first all-new jet since 1995, was unveiled in July this year.
It is the only big commercial aircraft made mostly of carbon fibre rather than aluminium and is billed as the most environmentally-friendly commercial jet ever built.
Boeing says the 787 is much more fuel efficient than its competitors and produces 20% less carbon dioxide.
Ironically, Airbus is due to deliver its first completed A380 to Singapore Airlines in the next few days, having incurred billions of dollars through a series of delays.