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SESK: Stuff Everyone Should Know · sesk.info/ifr-alt-2000-mountain

With no published minimum, how high above the highest obstacle within 4 nm must you fly IFR in designated mountainous areas?

2,000 feet.

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  1. 1,000 feet
  2. 2,000 feet ✔
  3. 500 feet

Why: 91.177 sets 2,000 feet above the highest obstacle within 4 nautical miles in designated mountainous areas. Elsewhere it is 1,000 feet.

Huh, didn't know that: Mountainous areas are designated in part 95.

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Why are mountains so funny? Because they are hill areas.
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References

Answer: 2,000 feet. 91.177 sets 2,000 feet above the highest obstacle within 4 nautical miles in designated mountainous areas. Elsewhere it is 1,000 feet.

  1. 14 CFR 91.177 Minimum altitudes for IFR operations www.law.cornell.edu/cfr/text/14/91.177
    an altitude of 2,000 feet above the highest obstacle within a horizontal distance of 4 nautical miles
    Checked 2026-10-10.

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