Final answer:
A Federal Air Marshal or Sky Marshal is responsible for onboard security during flights. They address safety and security incidents, different from the pilots' safety checklists. Post 9/11, the intensity of security increased, leading to higher opportunity costs due to longer waiting times at airports.
Step-by-step explanation:
The individual responsible for the safety and security of a flight and its passengers during flight, and who handles security-related incidents onboard, is known as a Federal Air Marshal or Sky Marshal. Although pilots also follow detailed checklists to ensure the safe operation of the aircraft, the Federal Air Marshal's specific role is to be vigilant and ready to deal with any threats to security while in the air.
This role was highlighted following the terrorist hijackings on September 11, 2001. After these events, airline security screening measures were significantly increased, leading to a rise in the opportunity cost for passengers, who now spend more time waiting at airports.
The cost for having a Sky Marshal on every flight is substantial, roughly $3 billion per year, adding to the financial implications of enhanced airline security measures.