Cellphone chats at 35,000 feet? US considers legalizing them on airline flights.

Hold on - fasten your seat belts, and put those tray tables up: Come May, the Federal Communications Commission plans to auction off some of the last remaining spectrum to companies that want to provide cellphone service at 35,000 feet.

While polls show the vast majority of Americans are opposed to in-air phone chatter - almost 70 percent in some surveys - technological innovations and market forces appear to be moving the nation's regulatory framework toward approving it. The FCC has said it could allow the service as early as next year. The Federal Aviation Administration has signaled that as long as airlines are confident it poses no safety threat, it would be in favor of lifting the ban as well.

Yet those who cherish cellphone-free flying sanctuaries still have hope. A study published this month found that - counter to what many Americans believe - cellphone radio signals do "present a clear and present danger" by interfering with sensitive navigational equipment.

"We're not trying to be alarmist, but we are saying, 'Let's just go slow to be sure there is no danger,' " says Granger Morgan, a coauthor of the study and head of the Department of Engineering and Public Policy at Carnegie Mellon University in Pittsburgh.

He and a colleague are the first to have actually measured the level of radio waves on 37 flights. Their findings were surprising. On average, one to four passengers use a cellphone on each flight, despite regulations forbidding it. And the signals emitted did cross over into the spectrum used by the Global Positioning Satellite systems that many planes use. While the interference was "random, sometimes hit or miss," says Professor Morgan, it was significant enough to cause problems when landing.

But advocates of allowing cellphone service say that technological innovations can overcome that. Two European airlines are already experimenting with a "pico cell" system that experts say allows cell signals to remain low enough so they wouldn't creep into other services' radio spectrum. It would do that by collecting the chatting passengers' signals at a central location within the plane and shifting them to a transmitter outside the aircraft.

A nonprofit advisory group, RTCA Inc., has been charged by the FAA with making a final recommendation on the safety of in-air cell use. Its report is due out in December. Many advocates expect it will find that new technology can overcome any serious problems.

If that happens, companies like aircraft manufacturer Boeing will be ready to move ahead with the technology.

"There's a disconnect: The market forces are moving this forward, and yet, the embodiment of market forces, [the flying public], is opposed to it," says Kevin Mitchell, chairman of the Business Travel Coalition in Radnor, Pa. "I really can't find a business traveler that thinks this is a good idea."

But another business travel group, the Association of Corporate Travel Executives, says that more than half its members would like to see the ban lifted. Its president argues such a move could add millions of dollars to the economy by allowing business travelers to use their time more efficiently.

Ultimately, if the FAA and FCC both approve the use of cellphones, it will be up to the individual airlines to decide whether to allow their passengers to chat.