Boeing admitted today that the 787 Dreamliner will be delayed by six months as it struggles to assemble the revolutionary new aircraft.

The 787 is currently the largest industrial project in the world with orders worth over $120 billion and the delay is likely to cost Boeing heavily in compensation payments to customers.

The company said that first deliveries of the aircraft will now be in late November or December 2008 rather than May 2008.

This is devastating for All Nippon Airways, which was due to receive the first aircraft. The Japanese carrier was hoping to have the 787 in its fleet in time for the Beijing Olympics, which would have given it maximum exposure.

Last month, Boeing said that it was delaying the first flight of the 787 until some time between mid-November and mid-December.

The first-flight target had already slipped from the end of August to September and will not now take place until May next year.

When the first-flight delay was revealed last month aviation analysts were sceptical that Boeing would be able to stick to its original delivery date as it squeezed the regulatory certification period down to just six months.

Further production delays have now forced the company to shift not only its first flight date but also delivery dates.

However, the tight certification period remains and analysts warned yesterday that further delays were still possible if any problems emerged when flying the plane.

The effects of the delay will be felt by dozens of airlines, possibly including British Airways, which announced two weeks ago that it was buying 24 787s.

BA is expected to start receiving the aircraft in 2010 but this may now be forced into 2011 or even 2012.

If there are further delays BA may struggle to receive its aircraft before the London Olympics in 2012, which would be a massive blow to the airline’s marketing and operational plans.

The 787 announcement comes just a week before Airbus finally delivers the first of its A380 superjumbos.

Airbus, the European aircraft manufacturer, has barely recovered from a two-year delay to the A380 programme, which cost it billions of euros in compensation and billions more in lost earnings.

One analyst said: “The 787 delay is possibly the best thing that has happened to Airbus all year. It’s a reminder that these things never go according to plan.”

The 787 is being assembled in Seattle with carbon-fibre fuselage sections imported from all over the world being fastened together using special clips.

The untested construction method has proved problematic, not least because of a lack of fasteners.

Jim McNerney, chief executive of Boeing, said: "We are disappointed over the schedule changes that we are announcing. 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 787 is a mid-sized plane that will become a mainstay of the global longhaul fleet. Its lightweight carbon-fibre fuselage will allow it to cut fuel consumption by about 20 per cent, reducing airline costs and also carbon dioxide emissions.

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