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In uncontrolled airspace below 18,000 feet, which IFR cruising altitude fits a magnetic course of 090?

5,000 feet, an odd thousand.

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  1. 5,000 feet ✔
  2. 6,000 feet
  3. 4,500 feet

Why: Under 91.179, IFR in uncontrolled airspace below 18,000 feet uses odd thousands for magnetic courses 0 to 179 and even thousands for 180 to 359. In controlled airspace you fly the altitude ATC assigns.

Huh, didn't know that: The rule does not apply in a holding pattern of 2 minutes or less or while turning.

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References

Answer: 5,000 feet. Under 91.179, IFR in uncontrolled airspace below 18,000 feet uses odd thousands for magnetic courses 0 to 179 and even thousands for 180 to 359. In controlled airspace you fly the altitude ATC assigns.

  1. 14 CFR 91.179 IFR cruising altitude or flight level www.law.cornell.edu/cfr/text/14/91.179
    any odd thousand foot MSL altitude
    Checked 2026-10-10.

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