What should the commander do if usable fuel remaining on arrival is less than the required alternate fuel plus the final reserve?

The correct response in this scenario is to divert to any adequate aerodrome for safe landing. When the usable fuel remaining upon arrival is less than the combined requirement for alternate fuel and final reserve, it indicates that the aircraft will not have sufficient fuel to safely reach its destination or to comply with regulatory requirements for fuel reserves. The primary goal is to ensure safety, and diverting to an adequate aerodrome allows the commander to land safely without the risk of running out of fuel.

Selecting this option prioritizes safety by identifying an alternative landing site where the aircraft can safely land before fuel levels become critically low. This is aligned with standard aviation protocols that emphasize a precautionary approach when fuel reserves are inadequate.

Other choices involve actions that either do not address the fuel shortage adequately or could increase the risk of an unsafe situation. For instance, proceeding to the destination aerodrome would not be responsible as the fuel levels would not support safe operation to that point. Adjusting performance to land with a minimum of 15 minutes of fuel also does not address the fuel deficiency as it reduces the safety margin without ensuring sufficient reserves. Declaring an emergency could be appropriate in some fuel-critical situations, but the preferred course of action is proactive diversion to ensure safety rather than waiting