Overhead "no smoking" signs will be replaced by "no mobiles" messages on some planes next year when technology is introduced to make it safe for passengers to use mobile phones mid-flight.

Airlines are seeking ways to police potentially annoying on-board phone chat via symbols of a mobile phone crossed out, forcing passengers to switch off during take-off and designated "night" periods.

The company developing the satellite technology for Airbus planes also said cabin crew would be able to remotely switch off phones or disable their voice function, allowing travellers to just use text messaging and email during quiet times.

"It is envisaged that airlines will turn the voice capability off, for example on long-haul flight during the plane's "night'," a spokesman for communications joint venture OnAir said.

"Each airline is likely to develop different protocols for the use of mobile devices, in much the same way that different protocols have developed in different countries for the public use of mobile phones."

Airbus said it was pushing ahead with plans for trials of mobiles, blackberries and other devices on planes next year, despite heightened security following a suspected bomb plot in Britain and setbacks for on-board communications in the United States.

OnAir is a joint venture with Airbus and information technology systems provider Sita.

Air France KLM is expected to lead the way when it takes deliveries of planes trialling the service in 2007, while low-cost carrier Ryanair is also close to ringing up extra revenue from mobile phones.

LEVEL OF ANNOYANCE

However, other carriers said they might limit the service to text messages or ban it altogether, amid fears it will put passengers off travelling unless it can be policed properly.

British Airways said it was interested in the technology but was surveying its passengers to see what level of mobile phone use would be acceptable or "downright annoying."

Germany's Lufthansa was also cautious, saying it had not decided whether to allow mobile phone use on planes yet.

"The issue is how you would get around the problem of disturbing other passengers," a Lufthansa spokesman said.

An Air France spokesman said the first phase of its trials would only involve data services such as text messages with a second phase covering voice.

TAP Portugal and Britain's bmi also plan trial the technology.

In a consultation paper on the subject in April, UK regulator Ofcom warned: "The potential for increased levels of agitation from passengers is a factor to be noted."

But asked about the social cost of mid-air mobiles, the outspoken chief of low-cost carrier Ryanair Michael O'Leary said: "Why should I care if it is generating some money?

"People are in a confined space. People tend to not want to get into long and involved mobile phone discussions with people sitting around them. I think it will be more people sending texts," he told reporters.

Advancements in airline communications have been slow to take off, particularly in the United States.

Boeing Co (BA) said last week it would shut its loss-making Connexion unit, which allowed airlines to provide high-speed Internet service to passengers. The satellite-based service, for which Boeing failed to find a buyer, was too costly and few airlines signed on.

In June, Verizon Communications Inc. (VZ) said it was cancelling its on-board phone service by the end of the year.