The significant increases in security were in place long before 9/11. There was a small increase in the effectiveness of security measures post 9/11 but it is difficult to measure the effectiveness of them as most of the attack vectors used post Lockerbie have had to be quite unusual to evade the existing security checks.
Hijacking used to be common in the early days of commercial aviation and the airlines resisted the idea of security screening as it didn't fit the experience they wanted their customers to have. The occasional inconvenience of hijacking was a price they considered worth paying. That changed once the hijackers started killing people and planes were bombed mid-air.
Hijacking used to be common in the early days of commercial aviation and the airlines resisted the idea of security screening as it didn't fit the experience they wanted their customers to have. The occasional inconvenience of hijacking was a price they considered worth paying. That changed once the hijackers started killing people and planes were bombed mid-air.