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SESK: Stuff Everyone Should Know · sesk.info/ifr-hypoxia-altitude

At roughly what altitude do judgment, memory and coordination begin to suffer from hypoxia?

12,000 to 15,000 feet.

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  1. 12,000 to 15,000 feet ✔
  2. 5,000 to 8,000 feet
  3. Above 30,000 feet only

Why: The air is still 21 percent oxygen at altitude, but lower pressure means less oxygen gets into the blood. Night vision can degrade as low as 5,000 feet, but other significant effects usually start above 12,000 feet in healthy pilots.

Huh, didn't know that: Pilot performance can seriously deteriorate within 15 minutes at 15,000 feet.

The dad joke
Hypoxia checklist: breathe in, think clearly, repeat.
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References

Answer: 12,000 to 15,000 feet. The air is still 21 percent oxygen at altitude, but lower pressure means less oxygen gets into the blood. Night vision can degrade as low as 5,000 feet, but other significant effects usually start above 12,000 feet in healthy pilots.

  1. FAA Aeronautical Information Manual 8-1 Medical Facts for Pilots www.faa.gov/air_traffic/publications/atpubs/aim_html/chap8_section_1.html
    From 12,000 to 15,000 feet of altitude, judgment, memory, alertness, coordination and ability to make calculations are impaired
    Checked 2026-10-10.

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