What must be calculated at each checkpoint during flight planning?

Continuation fuel is a critical factor that must be calculated at each checkpoint during flight planning. This refers to the amount of fuel needed to reach the planned destination, plus any additional fuel required for potential contingencies such as diversions or holding patterns. It ensures that the aircraft can safely reach the destination without running low on fuel.

Calculating continuation fuel at each checkpoint allows pilots and flight planners to assess whether the fuel levels are sufficient, taking into account factors such as route changes, weather variations, and updated air traffic conditions. This assessment is vital to maintain safety and operational efficiency throughout the flight.

Flight time, weather conditions, and passenger load are important components of flight planning but do not specifically mandate recalculation at each checkpoint like continuation fuel does. They may be reassessed as needed, but they are not continuous requirements in the same way that monitoring fuel levels is crucial for ensuring safe operations during the flight.