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The Pilots Desk
US-FAA14 CFR 135.157

Oxygen equipment requirements

Read the official rule

This regulation sets oxygen equipment requirements for Part 135 operations based on aircraft type and altitude.

Unpressurized aircraft must carry oxygen for pilots per §135.89(a), plus for passengers when flying above 10,000 feet MSL for more than 30 minutes (at least 10% of passengers) or above 15,000 feet MSL (all passengers).

Pressurized aircraft need a 10-minute emergency supply for passengers above 25,000 feet MSL in case of depressurization. They must also meet unpressurized requirements if cabin altitude exceeds 10,000 feet. If pressurization fails, pilots need either §135.89(a) amounts or a 2-hour supply (whichever is greater). Passengers need oxygen above 15,000 feet MSL for one hour, or just 30 minutes if the aircraft can descend to 15,000 feet within four minutes.

All systems must let pilots monitor oxygen quantity and flow. Above 25,000 feet MSL, pilots must be able to select undiluted oxygen.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*

This is an original plain-English explanation for training and reference, not legal advice and not for navigation. Always rely on the current official rule linked above. Last reviewed June 20, 2026.