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AI.II.N.R1FAA-S-ACS-25 · Nov 2023Risk management

High altitude flight.

ACS element text (the applicant demonstrates understanding of)

High altitude flight.

Bottom line

Hypoxia is a state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs. For optimum protection, pilots are encouraged to use supplemental oxygen above 10,000 feet during the day, and above 5,000 feet at night.

FAA references

  1. AIM 8-1-2 (Effects of Altitude) — AIM Basic 2/20/25 w/ Change 1 (8/7/25) & Change 2 (1/22/26)
  2. PHAK ch. 17 (p. 17-3) — FAA-H-8083-25C (2023)
  3. AC 61-107, para. 2-7 — AC No: 61-107B
  4. 14 CFR 91.211 (Supplemental oxygen.) — eCFR current as of 2026-03-05
  5. PHAK ch. 17 (p. 17-4) — FAA-H-8083-25C (2023)
  6. PHAK ch. 7 (p. 7-37) — FAA-H-8083-25C (2023)
  7. AC 61-107, para. 2-9 — AC No: 61-107B
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