There are NO documented reports of malfunction of navigational or other instruments on aircraft due to personal electronic devices. The FAA has done studies and conducted investigations and they do not have a singledocumented case of interfence. (Lovely what you can learn from TV thses days) According to one report (in the NY Times, I believe), SwissAir reports one incident where the apparent interference not only stopped when electronic devices were turned off, it resumed when the pilot gave permission for people to start using them again. ``Documented'' is the wrong word. There have been plenty of cases of trouble attributed to electromagnetic interference; what's lacking is controlled studies that demonstrate an effect, as opposed to anecdotal evidence from the pilots of various aircraft.