The maximum cabin pressure altitude above which oxygen is required for flight is

• A. 15,000 feet MSL
• B. 18,000 feet MSL
• C. 20,000 feet MSL
• D. 12,500 feet MSL

Answer: (A)

When flying at altitude, the air inside the cabin has to provide enough oxygen for everyone on board. As cabin pressure altitude increases, the amount of oxygen available in the air decreases, which can lead to hypoxia if no oxygen is supplied. The rule sets the point at which oxygen must be provided to all occupants at 15,000 feet MSL. Above this cabin altitude, the air is thin enough that supplemental oxygen is required to prevent impaired thinking and other hypoxia symptoms. Since the cabin pressure altitude is the effective altitude inside the aircraft, once you exceed 15,000 feet, oxygen must be available for everyone on board.