Judge Anthony Ensor warned Neil Whitehouse, 28, from Mansfield, Notts, that he faced prison after a Manchester Crown Court jury convicted him of "recklessly and negligently" endangering a British Airways flight from Madrid to Manchester last September.

The jury had heard that Whitehouse, an oil worker, had repeatedly refused to switch off his phone after being spotted with it on the Boeing 737.

Experts said the plane's navigational systems could have been affected by radio waves from the phone even though no calls were made during the flight.

'Arrogant conduct'

Adjourning sentence for three weeks, Judge Ensor said: "It cannot be underestimated the alarm and concern your arrogant conduct must have caused the 91 passengers and crew on this Boeing 737.

"I believe that because of the seriousness of your conduct, a prison sentence must follow. However I shall keep an open mind."

Whitehouse was first asked by cabin crew to turn the mobile off after he was spotted typing "I love you" onto the text face.

When told it might interfere with navigation, he replied: "Why? Are we going to get lost?"

The judge called for the ban on mobile phones on aircraft to be reiterated. In the US and Germany, the use of mobile phones on planes was an offence punishable by imprisonment whether interference was caused or not, he said.

Whitehouse is understood to be the first passenger to be prosecuted under the 1995 Air Navigation Order. He was remanded on conditional bail until 21 July.