Anonymous
Answered June 8, 2016
There are several things to remember.
The first is that
GTE Airfone systems were common then. Of the 37 phone calls placed from flight 93,
35 were placed on the Airfone system. This was traceable not only to the particular aircraft, but to a specific phone in a specific row on that aircraft.
In 2001, a dominant (but declining) cell phone system was analog
AMPS system at 850 MHz with up to
3 watts transmission power on the mobile side. One ‘feature’ of the AMPS system was far greater range than today’s digital systems. The range on the ground was up to 40 kilometers. In an aircraft, this range was enhanced.
Digital cell systems can detect if your cell phone seems to be in an aircraft and will restrict your use of the cell phone in order to avoid cascading interference with cell phones on the ground. In 2001, this block did not exist for the AMPS system.
For those reasons, the Airfone system and the AMPS system, the cell phone calls were possible from Flight 93 but would not be possible today.