Line of sight..
The reason for banning cell phones on planes is line of sight. A few cell phones in the air could saturate a lot of towers all at the same time. It is the cell carriers that requested cell phones be banned for flights... as for take offs and landings... Pilots wear headsets and have multiple speakers in the cockpit. If you get some phones close to speakers they create a lot of irritating interference and could cause the pilot to miss information from the ATC at the most critical time (avoiding other planes during take offs and landings). There has also been a ton of research on electronic noise. All electronic medical equipment is very strictly regulated for electronic noise. No electronic device can emit too much noise and all of it has to be shielded as much as possible. I read a ton of papers on it when I worked for Hp/Agilent... Fascinating stuff... But that is the reason you have to turn off cell phones in hospitals. They don't want someone dying in the OR because some schmuck just had to feel overly important and take a call in the middle of a hospital. I'm ok with no cell phones on planes and no devices on for take offs and landings... We don't need them at those times and an ounce of prevention is well worth it.
