For turbojet aircraft under IFR, what is the minimum fuel requirement when an alternate is required?

The minimum fuel requirement for turbojet aircraft operating under IFR when an alternate airport is required is set to ensure that the aircraft can safely reach its destination, safely divert to an alternate if necessary, and have an additional margin of safety.

In this case, the correct answer indicates that the aircraft must have enough fuel to allow for 30 minutes of flight at cruise speed after the planned destination has been reached. This is to account for potential delays or diversions, ensuring that the aircraft can operate safely even under adverse conditions or unexpected scenarios.

While other options present different time frames for fuel reserves beyond the destination, the regulation specifically mandates a minimum of 30 minutes for turbojet aircraft, balancing the need for safety and operational efficiency. It is important for pilots to adhere to these requirements to ensure that they are adequately prepared for various in-flight contingencies, which is crucial for IFR operations.