What is the required fuel reserve for a turbine-engine-powered air carrier airplane upon arrival at a distant alternate airport?

The required fuel reserve for a turbine-engine-powered air carrier airplane upon arrival at a distant alternate airport is indeed based on the requirement of having enough fuel to hold for a certain period before landing. The correct answer specifies that the reserve fuel must account for a scenario of holding for 30 minutes at holding speed while at an altitude of 1,500 feet over the airport.

This requirement serves to ensure that, in the event that the aircraft cannot land immediately at the alternate airport, there is sufficient fuel to maintain a safe orbit above the airport while waiting for permission to land or until conditions improve. Holding at 1,500 feet is a standard practice, ensuring that the aircraft is at a safe altitude and position relative to the airport.

Other choices reflect different time frames or operational conditions that do not align with regulatory requirements for turbine-engine air carriers. Options that suggest other time frames or elevations do not meet the established safety regulations. Therefore, the requirement of a 30-minute holding period at 1,500 feet accurately captures the needed fuel reserves to prioritize safety and operational efficiency in commercial aviation.