Very similar areas, but not exactly the same as one would do to 'scientifically' test the hypothesis. I can tell you that at about 1000' I always started having weak signal issues, and that in airplane mode I got to 5000' without any issue. I have no idea why, as I do not understand the basics of transmission. I am not even sure what waves connect me with the aircraft. Is there a simple 101 explanation for a lay person? Could some of the cellular 'waves' interacting with the phone cause problems thus limiting my range?