Smartphones have very low RF transmissions these days compared to the old analog bricks. The biggest reason for turning on airplane mode is to avoid flooding towers with requests while you are relatively low. Back in the olde days, when someone asked why they couldn't use a cellphone in a plane, I would (on the ground) have them turn it on and make a call in the cockpit of my Cessna. The VOR needles would jump all over the place. Of course this was at about a foot away. In those days, towers were about 10 miles apart and phones had to be able to transmit almost 20 miles. I know because we used analog phones far offshore on our sailboat. Now we are lucky to get a voice signal a mile outside the harbor.
I recently tried to use my iPhone from the viewing area of the Sears (okay, Willis) tower in Chicago. No signal. Someone told me that if too many towers get your signal at once, they shut you off.
I recently tried to use my iPhone from the viewing area of the Sears (okay, Willis) tower in Chicago. No signal. Someone told me that if too many towers get your signal at once, they shut you off.