According to the guidelines, at what altitude must oxygen be provided to all occupants?

• A. Above 12,500 ft MSL.
• B. Above 14,000 ft MSL for crew.
• C. Above 15,000 ft MSL.
• D. Above 20,000 ft MSL.

Answer: (C)

When you reach cabin pressure altitude of about 15,000 feet MSL, everyone on board must have access to supplemental oxygen. This is because the thinner air at that height can cause hypoxia fairly quickly, even for healthy individuals, so the safety rule ensures that oxygen is available to all occupants rather than just the crew or for limited durations. The 15,000 ft threshold is the point at which the regulation shifts from restrictions on oxygen use for individuals (like crew only or limited-time use) to a universal requirement for every person on board. In practice, this means if you’re flying unpressurized and the cabin is pressurized above 15,000 ft, you must have oxygen readily available for every passenger and crew member.