Security measures for commercial flights have undergone significant changes over time. Today, travelers must present a boarding pass to access gates and undergo security screening controlled by the federal government. They must also be mindful of the contents of their carry-on bags.

This was not always the case, as security checkpoints were previously staffed by private contractors and had more lenient rules. The current security system was developed in response to various attacks and attempted attacks that exposed vulnerabilities in air travel.

Further details are available on how these changes came about and the events that led to the implementation of stricter security measures.