What is the passenger flight frequency from O'Hare?

The frequency of passenger flights from O'Hare Airport is indicative of its status as one of the busiest airports in the world. The correct answer reflects that flights are scheduled to depart approximately every 30 seconds during peak times. This high frequency is a result of O'Hare's extensive flight operations, which are managed to maximize the airport's capacity while ensuring passenger safety and efficiency.

The airport's infrastructure, including multiple runways and advanced air traffic control systems, allows for this rapid turnover of flights. This setup means that many aircraft can safely land and take off in a short period, facilitating a fluid and dynamic travel experience for passengers.

In contrast, the other choices reflect unrealistic or impractical frequencies given the operational logistics of a major airport like O'Hare. For example, if flights were to depart every minute or every minute and a half, that would not capture the full capacity of O'Hare's capabilities during busy travel times. Similarly, a frequency of every 15 seconds could lead to congestion on the runways and airspace, which is beyond what is manageable in real-world conditions.