FAA Ground School Practice Test

When must supplemental oxygen be used for flights above 12,500 feet MSL?

1. During all phases of flight

2. Only during descent

3. Flight time in excess of 30 minutes above 12,500 feet

4. Only for night flying

The correct answer is: Flight time in excess of 30 minutes above 12,500 feet

The correct answer is based on regulations regarding the use of supplemental oxygen to ensure safety in the aviation environment. For flights above 12,500 feet mean sea level (MSL), the requirement for supplemental oxygen is specifically that it must be used if the flight duration exceeds 30 minutes at that altitude. This is due to the physiological effects of reduced atmospheric pressure at higher altitudes, which can lead to a decrease in available oxygen and result in hypoxia, a condition that impairs cognitive and physical performance. The regulation is in place to protect pilots and passengers, ensuring that oxygen levels remain adequate during the critical phases of flight when operating above these altitudes for prolonged periods. While oxygen may be recommended during all phases of flight at higher altitudes, it is not a regulatory requirement unless the time spent at that altitude exceeds 30 minutes. Therefore, the use of supplemental oxygen is specifically tied to this duration, reinforcing the importance of understanding altitude physiology and compliance with safety regulations.