Reply #9: The issue is NOT speed but height

[happyslug]

Remember on the planes involved with 9/11 the planes had dropped from their normal flight height of over 20,000 feet to less than 5000 feet (This is so the pilots could use land navigation to get to their targets, you can use landmarks to navigate at 5000 feet or lower, but you can NOT at 20,000 plus feet). Thus the Planes used on 9/11 all dropped down to below 5000 feet.

At 5000 feet (i.e. less than a mile high) most cell phones on a plane can pick up on any cell phone towers in the area and thus work. At 20,000 plus feet the distance to the ground is to great(over four miles above the ground), at such height the plane itself has to have a cell phone "Tower" to transmit the Cell Phone calls to the ground.

Thus people on the four planes involved in 9/11 could use their cell phones. The planes were low enough for the cell-phone to connect to cell phone towers. On most planes the plane is to high to connect unless you have a cell phone "Tower" on the plane itself. It is the later that is being considered NOT connecting to the towers on the ground.