Originally Posted by nrunning24

As a former engineer at Boeing, there is almost nothing that a cell phone can affect. When you think of all the sources of EMI that are in the air, cell phones are the last of your worries. Airplanes these days are built to handle EMI much more severe (think solar storms etc.). There is one time that I would want to make sure that cell phones are off or in airplane mode, and that's an auto-land in CAT3 conditions (less than 100 ft vertical visibility). I have heard that its possible for phones to affect the Radio Altimeter reading which is what tells the autopilot how far off the ground you are (see the Turkish 737 crash in AMS for more info on why this is important).

Do I turn my phone on airplane mode during flight? Yes, but that's more to save battery having my phone constantly search for service.