Which of the following security measures was implemented immediately following 9/11?

Implementing metal detectors at their highest sensitivities was a crucial security measure enacted immediately after the events of September 11, 2001. Following the attacks, the focus on aviation security intensified dramatically. The detection capabilities of screening equipment were upgraded to minimize the risk of threats, particularly related to weapons and explosives, which were used in the attacks. This heightened sensitivity aimed to ensure that even the smallest metallic objects could be identified, significantly improving the safety of passengers and crew aboard aircraft.

This measure reflects a fundamental shift in airport security protocols, emphasizing thoroughness and vigilance in passenger screening. The objective was to build confidence in air travel safety, which had been severely compromised. Such heightened sensitivity would allow security personnel to identify potential threats more effectively and prevent dangerous items from being smuggled onto flights.

In contrast, measures such as relaxed screening procedures, increased flight duration, or decreased luggage checks were not aligned with the immediate need for enhanced security in the wake of the attacks. Instead, the post-9/11 approach focused on stringent and thorough checks to safeguard against future incidents.