Airbus Releases Plan for Giant, Long-Range Jet : Aviation: Double-decker plane would carry 850 people. Some in the industry doubt its feasibility.

European plane maker Airbus Industrie on Wednesday released its most detailed plans yet for a double-decker, long-range jet that would carry up to 850 passengers--and maybe even a gym.

The four-engine airplanes would cost about $8 billion to develop, with a price tag to customers of $200 million apiece, said Jean-Jacques Huber, project manager for the jets, so far dubbed the A3XX.

By releasing proposed configurations for the jets, Airbus was attempting to move a step ahead, at least on the public relations front, of rival Boeing Co., which is not yet convinced the airlines will be interested.

Boeing is nonetheless discussing possible cooperation on such a project with the French, German, British and Spanish members that make up the Airbus consortium.

“We deal in market reality--we’re not floating paper airplanes,” Boeing spokesman T. Craig Martin said.

Although jets with twice the capacity of existing long-haul airplanes sound alluring for coming decades when air traffic is forecast to double and then triple, many industry executives have their doubts.

But the plane’s size could give airlines freedom to build rooms on the bottom cargo deck that could be used as fitness centers, business areas or lounges the size of a small apartment, Huber suggested.

Routes into congested Asian airports are the most likely candidates for the big jets. But if airlines rely less on big hub airports, as they have over the Atlantic, critics say the big planes could become a costly boondoggle.

Airbus believes there will be a market for 1,000 of the jets it is considering. It hopes to complete a feasibility study by 1995, possibly launching the program in 1998 and putting the jets into the air in 2003.

The jets would have a range of 7,000 nautical miles or more.