I have always been aware that if a US carrier did not lock the door for takeoff, it was a $10,000 fine if an FAA inspector caught them. That was imposed in the 1970's after all the hijackings to Cuba and therefore well before Sept. the 11th hijackings. The rationale was that most hijackings occur soon after takeoff, so to keep the door locked then was paramount. Such behaviour now is foolish, and surely punishable by a much bigger fine?.
