What about if you are flying in an aircraft with no radio or navigation gear? I assume it is technically illegal but why should it be the case? I have never noticed but will have a go to find out if I use my mobile when airbourne will I be charged accurately for the call. When you consider the number of passengers that fly out of UK airports each year how many cases of mobile phones interfering with the aircraft systems are there? I would hazard a guess that 10% of passengers forget to turn their phones off. When I use my mobile phone near my computer, tv, toaster etc these items all operate perfectly normally, I hope that aircraft systems are more secure than any of these but maybe I am wrong.....