For what it's worth, flying small aircraft at 5k feet AGL I've found cell reception to be amazingly spotty, even over relatively urban areas. I'm not sure that passengers asking for cell phone use on commercial flights are going to be happy with the result.

I'm not sure what the big driver here - being in a metal-skinned aircraft doesn't help of course, but I also get the impression that even a Skyhawk moves fast enough that tower registration becomes iffy. There's a lot of my phone and iPad showing service appearing/disappearing at random. Sometimes I'll call the ATIS on my phone to get it before I round a mountain and it often takes multiple tries to get that call to connect, and then of course sometimes it drops right before I get the altimeter setting or something else I cared about.