This inquiry serves as a classic example of a Fermi question, named after the physicist Enrico Fermi, who was adept at making accurate estimations with minimal or no specific data. The goal is to evaluate your problem-solving abilities and your skill in making logical approximations. To respond to the question, you can follow these steps: Select an airport. It's advisable to pick one you know well or a major airport where data might be easily accessible or anticipated. Estimate the number of flights that arrive and depart from the airport each day. Estimate the average number of passengers on each flight. Multiply the total number of flights by the average passenger count per flight. Consider the airport staff who would also pass through metal detectors. If possible, adjust your estimates to account for individuals who might not be flying but still go through security (such as pilots, flight attendants, and airport personnel). Finally, provide an estimate based on these considerations. Keep in mind that the objective of this question isn't to arrive at an exact figure, but rather to evaluate your reasoning process when faced with an unfamiliar problem. Your methodology and the rationale behind your answer are what truly matter.

Let’s take a look at Los Angeles International Airport (LAX), which is among the busiest airports in the world. Reports indicate that approximately 700 flights depart from LAX each day. The typical capacity of an aircraft can vary between 150 and 300 passengers. If we average that out to about 200 passengers per flight, that results in roughly 140,000 passengers. Furthermore, we should consider the airport personnel. LAX employs around 59,000 individuals. Assuming that about half of them pass through metal detectors each day, that adds another 29,500 to our count, bringing the estimated total to about 169,500 people going through metal detectors daily at LAX.

Let’s take John F. Kennedy Airport (JFK) as an example. JFK is served by six airlines. If we assume that each airline operates about 100 flights daily, this results in approximately 600 flights overall. With an average capacity of around 200 passengers per plane, this totals to about 120,000 passengers each day. Additionally, there are about 37,000 employees at JFK. If we estimate that half of them, or 18,500, need to pass through metal detectors each day, this contributes to our overall count. Therefore, I estimate that approximately 138,500 individuals pass through metal detectors at JFK airport daily.