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VFR REGULATIONS 16 / LEARN · EXPLORE · CHECK

Supplemental oxygen

Use cabin pressure altitude, and watch the boundaries.

Checking your account…

Your learning goals

  • Apply three steps up.
  • Recognize the limits and exceptions that affect this flight.
  • Explain a decision using the scenario and supporting rule.

Three steps up

  • Above 12,500 through 14,000 feet cabin pressure altitude: required minimum flightcrew must use oxygen for the portion exceeding 30 minutes at those altitudes.
  • Above 14,000 feet: required minimum flightcrew must use oxygen for the entire time at those altitudes.
  • Above 15,000 feet: provide oxygen to every occupant; crew-use requirements still apply.

At exactly 12,500, this rule’s first threshold is not crossed. At exactly 14,000, the 30-minute provision still applies. At exactly 15,000, crew use is required, but the every-occupant provision says above 15,000.

14 CFR §91.211

Required does not mean optimal

Hypoxia can degrade judgment before you recognize it. These are legal thresholds, not personal guarantees. Use aircraft guidance, training, and earlier oxygen when appropriate, especially at night. A pressurized airplane uses cabin pressure altitude for these thresholds, not simply indicated flight altitude.

14 CFR §91.211

Pressurized-airplane recognition

Additional rules apply at flight altitudes above FL250 (including an emergency supply for each occupant) and above FL350 (pilot-mask provisions with specific exceptions). Those are separate from the three cabin-altitude steps. Get aircraft-specific training before operating there.

14 CFR §91.211

EXPLORE / APPLY THE RULE

Move across the oxygen thresholds

Oxygen steps: above 12,500 through 14,000 crew use after 30 minutes; above 14,000 crew use throughout; above 15,000 provide to all.>12,500–14,000Crew after 30 min>14,000Crew throughout>15,000Provide to all

Use the written rule and worked scenario to reason through the example.

One constant-altitude segment only. Do not reset accumulated time by splitting a real flight into several calculator entries. Additional pressurized-aircraft rules are not modeled.

FLIGHT SCENARIO

What would change your plan?

At a cabin pressure altitude of 13,000 feet, you plan 45 minutes. When must the required crew use oxygen?

  1. NoticeWhat does this situation require?
  2. VerifyWhat evidence is still missing?
  3. DecideWhat keeps an option open?
Compare your reasoning

For the portion beyond 30 minutes at those altitudes: at least the final 15 minutes in this simple example. Choosing to use it sooner may be prudent.

SUMMARY

Use cabin pressure altitude, and watch the boundaries.

For the portion beyond 30 minutes at those altitudes: at least the final 15 minutes in this simple example. Choosing to use it sooner may be prudent.

Before moving on, explain the decision in your own words: what would you verify, and what would make you change the plan?

PRACTICE

Flashcards and knowledge check

Six flashcards, then five questions with explanations.

Enable JavaScript for flashcards and the knowledge check. The lesson and scenario remain available without it.

Sources & lesson notes

Sources & lesson notes

  1. 14 CFR §91.211Verified against eCFR text current through September 15, 2026.

For U.S. private-pilot airplane study. Rules verified against eCFR text current through September 15, 2026, with linked FAA guidance. Scenarios isolate a rule; actual flight decisions require all applicable rules, aircraft limitations, and current information.