Mobile phones in ‘flight mode’ do not transmit in the strict understanding of the word. However any electronic device has an Intermediate Frequency, which oscillates. This is where the confusion arises. Any device with power going through its circuit ‘can’ cause interference via its IF. Many years ago this was not quite as clearly understood as it is today. So the consensus was to turn everything off. However as you are now seeing regulatory bodies have come to realise they offer no issues with aircraft systems and the move is to allow electronics to be more widely used on flights. FAs are generally taught to have devices turned off, and unless they are electronic engineers with a full understanding of such things it’s not unreasonable for them to demand you power it down completely. WiFi is already on aircraft with some airlines, and more will follow. Maybe even pico cells for mobile use – that will be a crying shame in my opinion, the last bastion of peace and quiet – but I still expect everything will remain required to be off while the fasten seatbelt signs are on for the foreseeable future. If in doubt turn it off, pressing a button for three seconds to turn it on after 15 minutes is hardly one of life’s trials.
