The time to fly to the alternate airport is based on a direct route from your destination airport to the alternate using the same performance profile as the rest of the flight and a cruise altitude appropriate to the distance to the alternate. The altitude to the alternate airport is automatically determined by evaluating the flight’s cruise altitude, aircraft performance, and distance to the alternate.
To account for a missed approach, potential holding, and another instrument approach, a fuel buffer is automatically added. As listed below, buffer fuel varies by aircraft type and is added to the fuel required to fly direct to the alternate airport.
- Jet and Turboprop aircraft add 5 minutes of buffer fuel for holding and enough fuel to fly an additional 30 nm.
- Piston aircraft add 5 minutes of buffer fuel for holding and enough fuel to fly an additional 15 nm.
- There is no fuel buffer added when planning with a helicopter.