Instrument Flight Rules (IFR) Practice Exam 2026 – The All-in-One Guide to Master Your IFR Certification!

In unpressurized aircraft operations at altitudes between 12,500 feet and 14,000 feet, the regulations stipulate that pilots must use supplemental oxygen if the flight duration exceeds 30 minutes. Specifically, the required use of supplemental oxygen for the crew is partial, based on the flight duration at those altitudes.

For flights of more than 30 minutes but less than 12,000 feet, the required oxygen usage increases—for the time spent above 12,500 feet, crews must use supplemental oxygen for a specific fraction of the flight. The rule is that for every hour up to 14,000 feet, the crew is required to use oxygen for the first hour of the flight. After that, the requirement decreases, and they need to use supplemental oxygen for 30 minutes if flying for more than 1 hour but less than 2 hours.

In the case of a flight lasting 2 hours and 20 minutes at these altitudes, the crew must utilize supplemental oxygen for a total of 1 hour and 50 minutes. This reflects the need to comply with regulations that balance safety with the operational characteristics of an unpressurized flight environment. Hence, the answer provided reflects adherence to the required regulations regarding oxygen usage in such