At what cockpit altitude does the CKPT ALT light typically activate?

The CKPT ALT light is designed to alert the pilot when the cockpit altitude (the pressure altitude inside the cockpit) exceeds a certain threshold, indicating potential loss of cabin pressure. This light typically activates at an altitude of 19,000 feet mean sea level (MSL).

Understanding the function of the CKPT ALT light is crucial for flight safety, as it serves as an early warning for the crew to take appropriate actions, such as descending to a lower altitude or using supplemental oxygen, to avoid hypoxia or other altitude-related problems. This specific activation altitude is established based on physiological considerations, reflecting the point where the risks associated with insufficient cabin pressure start to significantly increase for crew members.