In the months following the attacks, physical security in airports around the world, and particularly in the US significantly tightened. The TSA immediately launched a comprehensive aviation security program and passenger and luggage screening became a major priority.
As the years have passed, technological advancements have led to the implementation of advanced passenger screening systems. The provision and requirement of Advance Passenger Information has become almost industry-standard across the world and security training has also been stepped up.
There are still threats to security on an international scale, but there is no doubt that the events of 14 years ago today have strengthened our resolve to never let it happen again.