Boeing''s new carbon-composite 787 Dreamliner plane may turn out to be unsafe and may lead to more deaths in a crash, says a report by controversial veteran journalist Dan Rather.

The new plane is mostly made from carbon composite materials that, though very strong, are inherently more brittle, rather than the more traditional aluminium alloys, which are more flexible. Sceptics say that this means it is more likely to shatter on impact and may emit poisonous chemicals when engulfed by fire.

Rather''s report is based on interviews with former Boeing engineer Vince Weldon as well as various industry experts, a transcript of the show indicates. "The problem is all the unknowns that are being introduced and then explained away as if there is no problem," Weldon is supposed to have said in an interview to be broadcast as part of Rather''s report.

Weldon compares a recent crash in a standard aluminum plane, where the dented but intact fuselage kept fire at bay and allowed the passengers to leave the plane alive. In a composite airframe, the fuselage would not crumple. It would shatter. The shattered hole would enable the fire to get into the airplane. Weldon says this means fewer people getting out, and more deaths.

The engineer says Boeing fired him after a 46-year career because of his persistent complaints about the design of the 787. He claims that others at Boeing share his views, but are afraid to speak out. Boeing did not permit its officials to go on camera for Rather''s report. But it said on Tuesday that Weldon''s claims were not valid, and that the plane would not fly if it were not safe.

A Boeing representative said the company had looked into Weldon''s claims, and technical committees had reviewed them. It said the materials it plans to use were "absolutely" safe, that they had been tested, and were sure to be certified by the US Federal Aviation Administration (FAA).

Unless the FAA finds the 787 to be as crashworthy as aluminum planes, it will not award the aircraft its certification. The plane, said Boeing, was doing well in those tests so far. The company declined to comment on the circumstances of Weldon''s departure from Boeing.

In Rather''s report, Weldon and other experts will argue that the 787''s carbon-composite fuselage would not survive a lightning strike as well as aluminium could, would emit toxic fumes if set on fire, and could easily be damaged without any visible sign.

Weldon says Boeing is misrepresenting the ease of maintenance of carbon fuselage planes to its airline customers. Other experts cite problems with carbon parts on Airbus planes, which had faults that were not easily visible.

But the report also includes aviation experts who see little or no problem with the 787''s carbon airframe. This includes Joseph Rakow, an engineer at consulting company Exponent Inc, who says he is "excited" to fly in a carbon composite aircraft. Todd Wissing, a commercial pilot, says he would fly the 787 as long as the composite materials are rigorously tested.

Boeing''s lightweight, fuel-efficient 787 has become the most successful passenger plane ever launched. Its first test flight has been delayed by three months owing to a shortage of fasteners and problematic flight control software, and will now take place only between mid-November and mid-December.

The first 787 is to be delivered to Japan''s All Nippon Airways in May next year. This means it will have to complete all flight tests in just six months, a much shorter period than any previous Boeing jetliner programme.

Boeing''s rival Airbus, owned by European aerospace company EADS, is also working on a composite fuselage for its new A350 jet, but it is years behind Boeing in the design and production process.

The report by former CBS News anchor Dan Rather airs on ''Dan Rather Reports'', which is broadcast on HDNet, a subscription-based television channel that reaches only about 4 million Americans. Last year, Rather left CBS after a scandal over his reporting on President George W Bush''s military record.