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SESK: Stuff Everyone Should Know · sesk.info/ifr-fuel-45-minutes

Under 91.167, after reaching the alternate, how long must an airplane be able to fly on remaining fuel at normal cruise?

45 minutes at normal cruising speed.

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  1. 30 minutes
  2. 45 minutes ✔
  3. 60 minutes

Why: 91.167 requires enough fuel to reach the first airport of intended landing, fly to the alternate if one is needed, and then fly 45 minutes at normal cruise. This applies in IFR conditions.

Huh, didn't know that: Helicopters need only 30 minutes of reserve under the same rule.

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Why do instrument pilots love the 45 minute reserve? It's the only time fuel gauges say 'you've got time.'
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References

Answer: 45 minutes. 91.167 requires enough fuel to reach the first airport of intended landing, fly to the alternate if one is needed, and then fly 45 minutes at normal cruise. This applies in IFR conditions.

  1. 14 CFR 91.167 Fuel requirements for flight in IFR conditions www.law.cornell.edu/cfr/text/14/91.167
    Fly after that for 45 minutes at normal cruising speed
    Checked 2026-10-10.

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