They've got three security check points before getting to the airport, a file on pretty much anyone with a ticket. Trying to by a last minute ticket with cash is considered a red flag, and guarantees a visit by and long chat with security. Inside the airport, security is pretty much invisible, their personnel looked the same as the passengers. Over all a very good system, but it just couldn't be implemented in a large country.

The best thing for the U.S. would be to secure the cockpits with heavy reinforced doors, and for Americans to get stronger backbones. There's no way that a hand full of box cutter wielding men should have been able to take over a plane. A few of the passengers may have been cut in the process of taking them down, but I doubt if any would have been fatally injured.