At what cabin altitude should pilots start using oxygen?

Pilots are required to begin using supplemental oxygen at a cabin altitude of 10,000 feet to ensure their safety and maintain optimal cognitive function. At this altitude, the partial pressure of oxygen decreases significantly, which can lead to hypoxia, a condition where the body does not receive enough oxygen for its needs. By implementing oxygen use at this threshold, it helps to mitigate the risk of cognitive impairment and fatigue, allowing pilots to operate the aircraft safely.

At elevations just above 10,000 feet, continuous exposure without supplemental oxygen can begin to impact performance and decision-making. Therefore, the protocol of starting oxygen use at this level is a vital safety measure in aviation practices.