A number of professional pilots contacted by CNET.co.uk's sister site, silicon.com, have said the threat posed to flights by mobile phones is minimal and they are confident on-board technology will enable mobile calls to be placed safely.

They have, however, joined the growing ranks of detractors from the scheme who fear the effect mobile phones will have on passenger comfort and the harmony in their cabins.

"Obviously people have left their phones on during flights and airplanes haven't crashed as a result," said one pilot, from a large UK airline.

"My guess is that if there are more than 20 passengers on board there's a better than evens chance that at least one phone is active throughout the flight. More than 100 passengers and it's practically a certainty. Since we do not observe any serious problems that have arisen as a result, this would indicate that such problems are very rare, if not impossible, " said another pilot. 

One did say he had seen instruments doing "weird things" for which the electromagnetic interference from mobiles was one suggested cause. Others suggested interference with sound on radios has also been observed while many said the level of disruption is irritating but not dangerous.

"The main concern with mobile phones on aircraft is that as you leave the ground and get further away from the masts, phones switch to a higher hunting power which is fine for one or two but 300 to 500 all at max power could create a problem," he added.

He said newer phones with a flight mode, which stop searching when out of range, tend to stop hunting for a signal around 5,000ft, though older phones can continue throughout a flight. But on-board pico cells, which phones will connect to automatically, will ensure mobiles locate that signal and don't keep searching at high power.

"Someday this pico cell will fail, at which point all the active phones will automatically boost their signal to the max in a futile attempt to contact the nearest base station. This will be an excellent test of the aircraft's susceptibility to EM [electromagnetic] interference," cautioned one pilot.

"My guess is that nothing will happen," he added. 

Despite confidence in the technology and the fact that mobiles appear to pose little threat to the workings of the plane, many pilots contacted by silicon.com did express concerns about the wisdom of the idea.

"Imagine all those ringtones and people shouting down the phone -- imagine trying to get some sleep," said one pilot.

"The last thing I'd want to hear sitting on an aircraft is someone beside me on a phone," said another.

Those thoughts were echoed by another pilot who said the biggest concern may be the risk of increased air rage incidents as already nervous, uncomfortable or in some cases inebriated passengers take exception to a noisy neighbour.

Another added radiation may also be a health concern for passengers. "Think of the worst-case scenario -- 550 people on board the Airbus A380 using mobiles at the same time. Forget for the moment the interference to equipment, think about the radiation bouncing around in that tin can," he said.