Re the cellular coverage issue - we are finding that, perhaps counter-intuitively, cellular coverage can in fact be WORSE when you can see MORE telecom masts, though testing to determine the optimal installation is currently ongoing. Watch this space!
The handset will be hitting multiple masts, so probably flip-flopping between base stations. I vaguely remember reading a paper on the new ESN and how aircraft would be integrated. I think it required 100's more new and modified EE base stations handling aircraft at 500 - 10,000 ft, but it would need new specifically designed hardware for the airframes too. In theory, EE would be the better bet for in-air use, but I suspect access to these masts may well be restricted to ESN users.
The ESN was due to go live in 2019, it's looking more like 2026 now. Only 7 years late, pretty good going. The catchphrase when installing Airwave was "yesterdays technology, tomorrow", I wonder what the ESN one is now...
