What is the result of a decrease in altitude with a constant altimeter setting?

When a decrease in altitude occurs with a constant altimeter setting, the altimeter continues to reflect the previous altitude level rather than the actual reduced altitude. This situation leads to a false sense of altitude, as the pilot may believe they are flying at a higher altitude than they actually are.

This is particularly critical during approaches and landings, as the pilot's reliance on the altimeter for safety could result in incorrect decisions, such as risking a controlled flight into terrain or obstacles that aren't accounted for due to the misleading altimeter reading. Because of this potential for misjudgment, awareness of this effect is crucial for flight safety and operational effectiveness.

The other choices do not specifically relate to the result of a decrease in altitude while maintaining a constant altimeter setting, as they pertain to different aspects of flight performance or operational parameters.