bernardd

I don't think there's a significant risk that a cellphone or computer can in itself bring down a modern airliner, and I'd go so far as to suggest that the more modern the design, the less likely this is to happen.

I think the real issue is it takes maybe 3 or 4 simultaneous failures to cause an accident. If you think about the Turkish 737 that ploughed into the polder outside Schipol recently, it had a faulty radio altimeter, but it took at least a combination of this with a high initial approach, some unforgiving design of the auto power retardation system and (probably) some distraction of the crew before they got into a catastrophic condition. The point with shutting off sources of EMI is you're aiming to remove the risk of, for example, adding the straw that breaks the camels back by minimising interference with ILS, altimeter or SatNav systems - the aircraft can and often is flown with faults but the more problems that line up, the greater the risk of striking terrafirma.