Margin fuel
Fuel choice and management is a hell of a good discussion point, considering recent events.
"Extra" margin fuel is not at the complete discretion of the captain. If there are valid reasons why additional fuel is required, the captain must accept this position and correctly assess the various required amounts to arrive at "minimum fuel". The computer generated company flight plan fuel does not normally account for these additional fuel amounts, but the captain is compelled to do so.
The expert assessment of the actual amounts will depend on the experience and skill of the pilot. The expertly assessed additive is related to regulations and circumstances, and is not related to the profit culture of the operator.
Different pilots will have different expert assessments of the additive fuel required, but this does not mean the operator can influence a race to the bottom with incentives and disincentives. Perspectives might include sufficient fuel for a more distant alternate that is judged to be less busy when the destination is closed. Ideally, captain and operator could consult for the best solution.
The important point is that planned use, 5%, missed approach, then proceed to alternate plus 30 minutes is only sufficient under textbook circumstances. Other circumstances usually raise the minimum fuel required. This additive is required fuel, not extra fuel.
There are other considerations for a legally compliant flight, including conserving and continuing in-flight assessment of required fuel.
Last edited by autoflight; 24th Aug 2013 at 07:43.