CVTDog,
I had experience last year flying with Iberia from Barcelona, and just after take off, the CC announced that they believed someone had left their mobile phone switched on, as it was interfering with cockpit instruments. They actually got everyone to check their phones were switched off, and said they may need to return to the airport if the problem was not rectified.
I'm no technical expert, but I guess they wouldn't have done that for no good reason.
I guess the OnAir system gets around that by virtue of the way it works (maybe?)
I've a feeling if you search pprune, you will probably find a technical discussion of this has probably been done to death many times.
Here is one such previous thread;
http://www.pprune.org/forums/showthr...e+interference