Cell Phone Calls From 30,000 Feet
Flight 93 was the source of 13 reported cell phone calls. Some have suggested that such calls were not possible because of supposed problems in cell phone reception at altitude. However this has never been proved, and there is also a question about the altitude of the plane when the calls were made. The idea that the relatives of Flight 93 victims were the recipients of fake calls seems like a great way of alienating them from skepticism of the official story.
The red flag here might not be not the fact that there were cell phone calls from Flight 93, but the fact that there were almost none from the three other flights.