For a 2-engine jet from KLAX to KDEN crossing the Rocky Mountains, what must be considered?

• A. The flight may need a drift-down alternate, depending on route and weight
• B. Only fuel
• C. Only pilot preference
• D. Weather at departure only

Answer: (A)

In two-engine jet planning, engine-out performance and where you could divert are essential, especially when crossing high terrain. The concept of a drift-down alternate comes into play when you’re evaluating whether you can safely reach an alternate airport after an engine failure and still have enough fuel and altitude to operate.

For a flight from a low-lying departure to a mountainous route like the Rockies, you must consider if, with one engine inoperative, you can maintain a safe flight path and reach an alternate. If the route, aircraft weight, and winds mean you might not be able to descend to a suitable altitude and still reach a reachable alternate, you need to plan a drift-down alternate. In other words, the flight may require a drift-down alternate depending on route and weight.

That’s why just thinking about fuel, or weather only at departure, or pilot preference isn’t sufficient—engine-out performance and diversions to a drift-down alternate drive the planning.