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FAR 91.179 and IFR cruising altitudes in controlled airspace above FL410

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Airspace, FAA Regulations, Instrument Rating

I am looking in the FAR’s for IFR Cruise Altitudes above FL410.  Of course I went to FAR 91.179 and AIM 4-6-2 to find my answer.

What I noticed now has me and some other pilots puzzled unable to provide an answer.

 1.  91.179 (b) title is “In uncontrolled airspace”.  When under the same section 91.179 (b)(4)(i) refers to Flight levels above 29,000 ft.

  • I don’t know of any airspace above FL 290 that is uncontrolled.
  • It would make more sense if the title of section b were to read “In controlled and Uncontrolled”.  then I would feel more this regulation applies to flying at any FL above 18,000 in “controlled” airspace.

2.  91.179 (b)(3) reads - When operating at flight level 290 and above in “non-RVSM airspace”,

  • RVSM airspace begins at FL290.  How can there be non-RVSM airspace above FL290

The ultimate question here is:  Where is the source information where I can find how the regulations want me to fly in the Flight Levels above 410 in “controlled” airspace.

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2 Answers



  1. Kris Kortokrax on Apr 08, 2023

    For any controlled airspace, you refer to 91.179(a).
    The extents of U.S. airspace are defined in Part 71.

    Class A extends from FL180 to FL600, in the areas defined by 71.33.

    Class E is defined in 71.71 and includes airspace above FL600 (with no upper limit and within the defined areas).

    For 91.179(b), you have to think globally.

    91.703(a)(3) requires that when over the high seas or in a foreign country, you comply with Part 91 (excepting 91.9117(a), 91.307(b), 91.309, 91.323 and 91.711) as long as it is not inconsistent with the regulations of the foreign country or ICAO Annex 2, when over the high seas.

    91.179(b) is worded that way to account for a situation where you might be over water or in a foreign country where there might be uncontrolled airspace above FL290.

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  2. awair on Apr 10, 2023

    RVSM airspace is FL290-410.

    Also, when traffic is less dense, ATC may approve blocks or non-standard levels.

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