Having read through two threads about technology in-flight, I was reminded of a very peculiar practice on PR: all electronic devices must be turned off and not be used during the flight. Seems normal, right?
But there's more: they must be turned off and not be used during the flight...even in flight mode. As far as I know, PR is the only airline that does this, and to this day I still don't know why. (Curiously, they don't enforce it, but they do sometimes: I was asked to turn my mobile phone off, but I responded that it was in flight mode, and the F/A said "even in flight mode".)
So this thread's question is pretty simple: how effective is flight mode in reducing and/or preventing interference during a flight, and do devices that have flight mode enabled still pose an interference threat to in-aircraft systems?