FAA Ground School Practice Test

What is the maximum cabin pressure altitude a civil aircraft can be operated at without providing supplemental oxygen to each occupant?

1. 12,500 ft MSL

2. 14,000 ft MSL

3. 15,000 ft MSL

4. 18,000 ft MSL

The correct answer is: 15,000 ft MSL

The maximum cabin pressure altitude at which civil aircraft can be operated without supplying supplemental oxygen to each occupant is 15,000 feet MSL. This regulation is crucial for ensuring passenger safety and comfort. At pressures above this altitude, the partial pressure of oxygen in the air decreases, which can lead to a condition known as hypoxia. To mitigate the risks associated with reduced oxygen availability, the Federal Aviation Administration (FAA) mandates that supplemental oxygen must be provided to each occupant if the cabin altitude exceeds this level. While there are provisions for other altitudes for certain scenarios—such as for flight crew or when the aircraft is above 12,500 feet but below 14,000 feet, where only the crew requires oxygen after 30 minutes—the definitive threshold for all occupants is firmly established at 15,000 feet MSL. Thus, understanding this altitude limitation helps pilots and operators ensure the safety and well-being of everyone on board during flight operations.