Airplane accidents existed before 9/11 and it was never a motivation to identify who is flying, so that's not it.
Remember that before 9/11 a flight ticket was just a physical ticket like any other. You'd buy it and could sell it forward or give it away to whoever and they could use it by just showing it. Nobody cared who it was, just that everyone boarding had a ticket.
Remember that before 9/11 a flight ticket was just a physical ticket like any other. You'd buy it and could sell it forward or give it away to whoever and they could use it by just showing it. Nobody cared who it was, just that everyone boarding had a ticket.