A JUMBO jet changed direction because of interference from a passenger's mobile phone, air safety officials have told The Scotsman.
The revelation came as the Civil Aviation Authority (CAA) attempted to avert a surge of air rage incidents involving mobiles by warning holidaymakers that most airlines do not yet permit their use in flight.
Ryanair is among a few carriers that have equipped some aircraft with the necessary technology, but the CAA fears passengers may think it is already widespread.
The authority said police had been called to several incidents after passengers became abusive or violent to cabin crew when told to switch off their phones.
It has commissioned research that showed mobiles could affect aircraft navigation and communication systems, "producing significant errors on instrument displays and background noise on pilot radios".
The CAA said pilots had complained that interference from mobiles had distracted them, caused noise in their headphones and triggered false warnings, such as smoke alarms.
Incidents have included the speed and direction of a Boeing 747 being changed by a passenger using a phone after the aircraft took off from Miami in February last year.
A CAA report said the pilots were forced to change the controls after the plane's speed and direction changed three times.
It stated: "During climb, pilot intervention was required on three occasions to prevent speed exceedance and to ensure correct tracking after the aircraft turned right when a 'direct to' command required a left turn.
"A passenger on the upper deck was observed using a mobile phone and very reluctant to turn it off. The crew … suspect that its use was the probable cause of the control problems."
In another incident, at Edinburgh airport in February, a passenger became abusive and disruptive in a row over the use of a mobile phone aboard a Boeing 737 as it was taxiing to the runway for takeoff.
Aircraft equipped for passengers to use their mobiles in flight have the equivalent of a phone mast on board, which safely channels phone signals. Without this technology, a handset being used to make a call would attempt to reach a mast on the ground, causing it to transmit at maximum power. This could cause harmful interference with aircraft equipment.
The CAA said Bmi, Air France, TAP Portugal, Qantas, Emirates and British Airways were among airlines operating or planning mobile phone trials, but even regular travellers would rarely fly on the few equipped aircraft.