A delay of seven to 12 weeks in the first Boeing 787 Dreamliner flight has set off speculation among aviation analysts that Boeing may not be able to deliver the pioneering all-composite airliner to its first customer as scheduled next May.

Boeing executives, however, insist that they will be able to meet the timetable. They hope to speed up the flight trials by creating a larger team of test pilots, who will fly the new passenger jet round the clock.

The first flight will be seven to 12 weeks later than Boeing announced when it rolled out the jet in July, company executives told the media in a conference call on 5 September.

The present postponement comes on top of a one-month delay announced earlier.

The Dreamliner now is expected to make its first flight sometime between mid-November and mid-December, rather than at the end of September or early October. Boeing says the delay is because of temporary issues, and that there are no major flaws in the company''s worldwide network of partners that supply entire sections of the jet.

But analysts are now being sceptical about Boeing''s assertion that the first 787 will still be delivered to Japan''s All Nippon Airways in May 2008. Boeing also admits that its revised schedule leaves almost no room for manoeuvre if any significant problem turns up during flight testing.

What compounds matters is that the aircraft is technologically different. No significant problems are anticipated, but if something goes wrong in the Federal Aviation Administration (FAA) certification process, then it is virtually certain that the programme will face damaging delays, like Airbus faced earlier with the A380 super jumbo.

Boeing has a schedule crunch ahead. It has to complete not only the first plane, but several others needed to perform the rigorous flight tests required by the FAA. What is more, the company admits that it needs the extra weeks to finish structural work on the first plane that haven''t been completed by its airframe partners in Italy, Japan, Kansas and South Carolina. It also has to integrate the flight-control software code supplied by the Phoenix-based Honeywell aerospace.

The partners are now being given more time to build and equip their sections of the planes that follow the first one. But to achieve delivery in May, the time available for flight tests has shrunk from nine months to around six months. Boeing plans to get around this by operating its flight tests on an intensive schedule, with a team of 34 test pilots, 24 hours a day, seven days a week.

After first flight, additional aircraft have to join the test programme at the rate of one every two or three weeks, until there are six jets in test flights. Each is now scheduled to fly about 120 hours a month, compared with 70 or 80 hours a month on the earlier Boeing 777 test flight programme. This means that if any major issues surface during flight-testing that require any sort of redesign or rework in the airplane, it may mean putting off the final delivery schedule.

What went wrong?

The Dreamliner is assembled at Boeing''s Everett facilities from large sections built around the world. Months ago, Boeing has admitted that the first sections arriving for final assembly were missing most of their interior systems, and some had thousands of temporary fasteners holding the pieces together.

This meant Boeing technicians at Everett had to do work that ought to have been completed by the supply partner. This was easier said than done. One major complication was that some of the partners had inadequately or incorrectly documented their work. This meant working on a trial-and-error basis, which took up a lot of time. For example, over 700 temporary fasteners are still to be replaced on Boeing''s first 787.

Last year, Boeing announced triumphantly that trials of the 787 flight-control software had gone off very well during flight tests on a leased American Airlines 777.

But on Wednesday, the company revealed that Honeywell has incurred heavy time overruns in writing, testing and certifying the flight-control software code, because the scope of work was underestimated. The software is now scheduled for delivery to Boeing''s test labs "later this month".

While a two- to three-month delay in delivery of the Dreamliner to its first customers would have a minimal financial impact on Boeing, but the delay is likely to add substantially in terms of costs, as Boeing throws people and resources at fixing the problems.

The company says this won''t affect its bottomline, because previously announced increases in 787 R&D spending have left room for such costs. What will cause trouble is if the delay gets extended to six months or more.