The battle over mobile phone standards may be kicking off again - this time in the sky.

It is widely accepted that the GSM standard won the battle on the ground worldwide thanks to its wide deployment, and now it is planning to extend that into airplanes. However, the US standard CDMA is already there.

A European consortium calling itself the Wireless Cabin will soon begin tests on a new service that will allow airline passengers to make calls on flights with mobile phones - based on GSM. The test, however, follows a similar in-flight telephony trial based on CDMA, conducted by American Airlines and Qualcomm last month in the US.

The Wireless Cabin began in August 2002 as a collaboration between several European equipment manufacturers and research institutes, including Airbus Deutschland, the German Aerospace Center (DLR), Inmarsat, Siemens and Ericsson. Its goal is to provide airline passengers with several wireless services, including mobile phone telephony, broadband wireless LAN and short-range Bluetooth.

The technologies of choice for the in-flight mobile phone service are circuit-switched GSM and packet-switched UMTS - the 3G technology supported by GSM operators and equipment manufacturers. The service will be working "this year", according to Josef Kolbinger, business director of Siemens' GSM radio infrastructure unit, which is supplying wireless access equipment for the project.

The American Airlines-Qualcomm test, on the other hand, was approved by the US Federal Aviation Administration (FAA) and the Federal Communications Commission (FCC), two agencies that still prohibit the use of wireless phones on flights. The trial was aimed at easing their concerns over the possibility of mobile phones generating radiation that could disrupt a plane's on-board navigational equipment.

Radiation is also one of several key issues being addressed by the Wireless Cabin project, according to Siemens' Kolbinger. Other issues include power supply, device sturdiness and size, and quality of service. Kolbinger said he doesn't expect to see a commercial in-flight mobile phone service launched based on the group's research before the end of 2005. "There's still plenty of development work to be done," he said.

That timeline, of course, will hinge on whether both the GSM and CDMA technology groups convince the FAA and FCC to soften their stance against mobile phones in flight.

Should the agencies give the green light, the market for in-flight mobile phone service could boom, according to Emma McClune, wireless analyst with Current Analysis Inc. "There's definitely a business," she said. "Airlines have a very captive audience. Many of their passengers will want to use the time to make calls and check e-mail."

They may, indeed, provided, of course, their phones are compatible with the airline's choice of wireless technology.