And you thought a six-hour flight delay was bad. Aerospace giant Boeing Co. said yesterday that it would be six months late delivering its new 787 Dreamliner jet to airlines.

In an embarrassing setback, Boeing said carriers wouldn't be able to start flying the highly touted Dreamliner until the end of 2008 instead of next May as originally scheduled. Most carriers won't see the plane until 2009 or later, Boeing said.

"We're disappointed we have to announce this delay," Jim McNerney, Boeing's chairman and chief executive, said during a conference call with Wall Street analysts. "We wish we didn't have to do this."

Boeing's fortune has been riding high on what has become the fastest-selling passenger jet ever. Built with composite materials, the plane promises to be more fuel efficient and easier to maintain than the current generation of commercial aircraft.

With the composite design, passengers are expected to have more comfortable cabins and bigger windows.

Boeing has orders for more than 700 Dreamliners, valued at more than $100 billion.

The delay in deliveries is not expected to have a material effect on Boeing's finances and will not change its earnings guidance for 2007 and 2008, company officials said.

Still, yesterday's disclosure was surprising, because officials until just a few days ago adamantly had insisted that the plane would be delivered on time despite reports that it was having difficulty resolving lingering production problems.

Wall Street didn't take the news well, and Boeing shares slid nearly $3 to $98.68 after rising steadily over the past year on booming sales of the new aircraft.

The delay evoked memories of troubles faced by Boeing's rival, Airbus, as it was developing the A380 superjumbo jet. The world's largest passenger jet — capable of seating 525 passengers — fell two years behind schedule. Instead of flying in 2006 as planned, it will make its inaugural flight this month.

The delay cost the European aircraftmaker billions of dollars, roiled relations between France and Germany, and led to the ouster of the company's top two executives.

"I certainly don't think it'll be two years, but you can't rule out the possibility of further delays," said Scott Hamilton, an aviation consultant in Issaquah, Wash. "I know that they are trying to say everything is going to be fine, but it's really what you don't know that will kill you."

Boeing officials took great pains yesterday to explain that the problems were being resolved and that the delay would give them time to address any additional problems that might pop up. Much of the delay was prompted by a shortage of fasteners and other parts needed to assemble the plane, Boeing said.

Major problems are "largely behind us," said Scott Carson, head of Boeing's commercial aircraft business.

Japan's All Nippon Airways, which ordered 50 Dreamliners and expected to be first to fly the plane in May, said in a statement that it regretted the delay but that it would work closely with Boeing to "keep the impact of the delay to a minimum." The airline had hoped to fly the Dreamliner for the Beijing Olympics next summer.