The blocks
Taxi fuel, trip fuel to destination, contingency (typically 5% of trip), alternate fuel to divert, final reserve (30 minutes holding for jets) and any extra the commander adds. The sum is the block fuel loaded.
Why reserves are legally fixed
Final reserve fuel may not be planned for use. Reaching it means declaring a fuel emergency ('MAYDAY FUEL'), which grants landing priority. Planning that consumes reserve is planning to break the rules.
Cost index
Airlines trade fuel against time using a cost index. CI 0 flies the most fuel-efficient speed; a high CI flies faster, burns more, and recovers schedule.
Key points
- Block = taxi + trip + contingency + alternate + final reserve + extra.
- Final reserve for jets is 30 minutes at holding speed at 1,500 ft.
- Cost index sets the trade-off between fuel burn and time cost.
Knowledge check