Which act clarified the responsibilities of airlines and airports regarding aviation security?

The act that clarified the responsibilities of airlines and airports regarding aviation security is the Aviation and Transportation Security Act, enacted in 2001. This legislation was a direct response to the events of September 11, 2001, and established the Transportation Security Administration (TSA) while significantly expanding the federal government's role in aviation security. It mandated new security measures for airlines and airports, laying out clear responsibilities for both sectors in ensuring passenger safety and the protection of transportation systems.

The other options, while related to aviation in various capacities, do not specifically address the regulatory framework for aviation security as comprehensively as the Aviation and Transportation Security Act. This act represents a pivotal shift in how security is managed within the aviation industry, ensuring that cohesive security measures are implemented across all airlines and airports.