The maiden flight of the new Boeing 787 Dreamliner could be delayed by several weeks, although its launch is still planned for mid 2008, the head of Boeing Commercial Airplanes said on June 17.

"The first flight is targeted for end-August but it will happen when the plane is ready. Frankly my guess is, it is going to happen mid-September," said Scott Carson on the eve of the Paris Air Show.

"In two weeks, we'll be revealing the 787 to the world," he said, referring to the first factory roll-out on July 8, adding, "We believe we are on track to deliver the first plane in May 2008."

Questioned about reports of problems regarding the aircraft's weight and sub-contracting, Carson said that "rumors of how difficult and serious challenges are exaggerated."

"Weight has been a challenge for some time. We are making very big progress, but there are still some efforts to make," he added.

With a range of up to 14,500 kilometers, the 787 will use 20% less fuel than any other plane of its size through engine improvements and the use of lighter composite metals for structure, Boeing says.

It is set to be the U.S. aerospace giant's biggest commercial success, with 584 orders confirmed since its launch in 2004, compared to just 13 for rival model the Airbus A350.

The success of the new plane has allowed Boeing to overtake Airbus as the world's biggest aircraft maker, based on last year's orders.

Boeing said that ahead of this year's Paris Air Show, it has twice as many orders as its European rival, with 429 compared to 201.

Among the potential 787 clients, Boeing is holding "preliminary discussions" with U.S. carriers Delta and American Airlines, Carson said.

Asked about Airbus chief executive Louis Gallois's call for Boeing to take part in an industry conference on protecting the environment, Carson said he shared his concerns.

Industry players should ensure they were all heading in the "right direction" in technological research, he said.