When must flight crew utilize supplemental oxygen?

Flight crews are required to use supplemental oxygen anytime the cabin altitude exceeds 14,000 feet. However, the correct choice indicates that the obligation to utilize supplemental oxygen arises at a cabin altitude exceeding 13,000 feet, which aligns with regulations designed to ensure safety in environments where lower oxygen levels can impair performance and cognitive function.

Exposure to altitudes above 13,000 feet can significantly affect crew members whose cognitive and physical abilities are critical for safe aircraft operation. Supplemental oxygen ensures that crew members remain alert and capable of performing their duties effectively under conditions that may otherwise lead to hypoxia—a condition of insufficient oxygen.

Thus, the regulation mandates the use of supplemental oxygen at this threshold to mitigate risks associated with altitude, ensuring that all crew members remain in optimal condition for managing flight operations. The other options may misstate the required thresholds or associated conditions under which supplemental oxygen must be utilized.