Reply #13: I looked at this

[Kevin Fenton]

http://physics911.net/projectachilles.htm

The experiment seems to have taken place over a built-up area of 300,000 people with dense networks of cells. The denser cells become, the less powerful the transmitters are and the harder it is to make a call from a plane - I suspect the problem is the urban BTS on the ground, not the phones. Rural transmitters should be more powerful, because they are less dense.