The RAF used to have this policy and announcements on their transport aircraft if they were carrying passengers. It amused me - the thought that an iPhone could be used to (theoretically) affect one of these aircraft. Who needs a big missile...

Many years back I was involved in the design and compliance of electronic equipment. Back in the 80's no one gave any thought to protecting and preventing RF interference and protecting devices from it. But then came the 90's and 2G mobile phones and everyone's 80's hi-fi started buzzing when the neighbour made a phone call. Of course it impacted many more important systems such as those on aircraft. Regulators woke up to the issue and mandated that all equipment must be adequately immune to RF interference (EMC) and not produce unacceptable levels of interference (EMI). From the 90's onwards just about every electronic product has some protection. This includes the systems in cars (you don't want ABS or airbags operating when you phone someone) and likewise aircraft. Of course we were still flying around in aircraft built with 80's electronics well into the new millennium. Anything more recent is highly immune to EMI.