Originally Posted by
EGLL_Director
I don't think it's a CAA rule. AA let you use your phone on the ground at LHR. If the CAA had it covered within a "CAP" document they wouldn't be permitted to allow this.
However rules are rules - and this is a very common one.
It's the FAA that regulates AA. But I think this is in fact a BA rule, maybe guided by the CAA.
It is all to do with the signals some devices give off interfering with the flight deck instruments and the radio. As mentioned the Captain can allow passengers to use devices if delayed on the ground with the engines still running.