(CNN) -- Boeing on Wednesday announced a third delay in delivery of its much-anticipated 787 Dreamliner, saying the aircraft will now be ready in late 2009.
Boeing's latest forecast delivery date means the 787 is 15 to 18 months behind schedule.
The announcement is widely seen as an embarrassment for the Seattle-based manufacturer, which cited supply and assembly problems for the latest postponement. When Boeing unveiled the 787 last year, it forecast a May 2008 delivery.
The Dreamliner's first customer, ANA of Japan, issued a statement saying the company is "extremely disappointed."
The 787 is a medium-size long-haul plane that is expected to become the backbone of airlines' long-haul fleets, replacing the Boeing 767.
Airlines such as Qantas, British Airways and Continental intend to use the 787 to open up new "long thin routes" -- long routes with fewer passengers than carried by the enormous 747.
Those long thin routes would bring new connections to cities that don't normally handle heavy long-haul traffic with flights such as Manchester, England to Denver, Colorado; Madrid, Spain to St. Petersburg, Russia; or Paris, France, to Nashville, Tennessee.
The latest forecast delivery date -- the third quarter of 2009 -- means the aircraft is 15 to 18 months behind schedule.
The Dreamliner has been a big success for Boeing in terms of orders -- it has received more than 700, a record for a new aircraft.
"We are extremely disappointed," ANA said in its statement. "We still have no details about the full delivery schedule. We would urge Boeing to provide us with a 120 percent definitive schedule as soon as possible."
Boeing officials said they are confident about meeting the new target date.
"Our revised schedule is built upon an achievable, high-confidence plan for getting us to our power-on and first-flight milestones," said Scott Carson, Boeing Commercial Airplanes president and chief executive.
"We deeply regret the disruption and disappointment these changes will cause for our customers, and we will work closely with each of them to minimize the impact," he said, adding the company is moving to improve its supply chain and production system.
Boeing is building the Dreamliner with new technologies and parts sourced from around the world. It is made of composite materials, not metal, meaning it is very light and offers greater fuel efficiency -- up to 20 percent better than current aircraft.
The delays mirror the problems that Boeing rival Airbus has had in delivering the A380 superjumbo, which suffered two years of delays and cost overruns before making its first flight last October.
"This is a deep embarrassment for Boeing, who had hoped to avoid the fiasco of the A380," said CNN Correspondent Richard Quest, who covers the travel and aviation industry.
The A380 and the 787 serve different needs for airlines and so are not in competition with each other -- though both have been the star aircraft for their respective manufacturers.
"It was never a question of either-or; it was a question of both," Quest said. "Airlines the size of British Airways will need the A380 to increase capacity, and the 787 to increase frequency on heavily traveled routes and open up new long thin routes."
The delays are another blow for Boeing after it lost out on a huge military contract with the U.S. Air Force in February.
The Air Force awarded a $35 billion deal instead to Northrop Grumman and its European partner, EADS, the parent company of Airbus, to start replacing air refueling tankers.
The move surprised many in the business industry who expected Boeing to be favored over the company that will use a European company's airframe, Airbus, for the tanker. E-mail to a friend