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Air travellers all know the familiar message over the PA system: "Please ensure all electronic devices are switched off ...."

One passenger on a US flight, however, decided to take the law into his own hands when he saw the instruction being ignored.

Russell Miller, 68, sparked a media storm in December after striking a teenager who refused to turn off his iPhone on an aircraft as it was about to depart Las Vegas for Boise, Idaho.

Today Miller pleaded guilty to battery in a US court.

Miller claimed the teen had continued playing with his phone after the crew had issued their instructions.

Miller said he did not "punch" the teen as the media reported, but "tapped him on the arm to get his attention".

The boy claimed that Miller hit him hard enough to leave a mark, but Miller disputed this.

Either way, the judge ruled that Miller had overreacted and overstepped the bounds by taking on the role reserved for cabin crew, the Idaho Statesman reported.

Miller was sentenced to 60 days in jail, 57 of these suspended, and ordered to pay US$275 in fines and court costs.