Last summer, on a flight from Washington National to Minneapolis (which would have been near the Flight 93 flight path), I checked my cell phone to see if I was getting a signal, and I did have a signal three times out of approximately 10 attempts. The third time, I decided to call my home phone (there was nobody home but it has an answering machine). I didn't want any hassle from the flight attendant, so I just quickly punched the speed dial and held the phone out of sight, then closed it after about a minute. When I got home, I had about 10 seconds of airplane noise on the answering machine.
When I mentioned this on the DU board, someone said, well, phones and networks are better now than they were in 2001. But my phone uses the same CDMA technology that I was using before 2001, and since the output power of cell phones has always been limited to 5 watts by law, not by technology, the only real difference between the phone I have now and the ones available then is that this one is about half the size. Undoubtedly, there are more cell towers now than there were then, which would certainly make a difference in the percentage of successes. But with 100% confidence, I can say that anyone who claims it's impossible to make cell phone calls from a passenger jet at over 30,000 doesn't know what he's talking about.