If you listen to the approach frequencies on a scanner near any large airport, you will quite often hear the distinctive "biddybip biddybip biddybip" of the GSM cell association - from switched-on phones right up there in the cockpit.
A good ten years ago now, however, I got a grumpy letter from Orange pointing out that my IMEI had been spotted at four mutually-invisible cell sites and presumably I'd been flying over a few thousand feet up. I had indeed been in the area in a motor-glider. Unfortunately since the cell sites weren't expecting to see the same phone from all the locations, the site controllers promptly crashed, taking out all the phone coverage in that area for a couple of hours. Oops.
But I don't want to shut off my e-reader - Boing Boing
If you listen to the approach frequencies on a scanner near any large airport, you will quite often hear the distinctive "biddybip biddybip biddybip" of the GSM cell association - from switched-on phones right up there in the cockpit. A good ten years ago now, however, I got a grumpy letter from Orange pointing out that my IMEI had been spotted at four mutually-invisible cell sites and presumably I'd been flying over a few thousand feet up. I had indeed been in the area in a motor-glider. Unfortunately since the cell sites weren't expecting to see the same phone from all the locations, the site controllers promptly crashed, taking out all the phone coverage in that area for a couple of hours. Oops.