In which situation would an increase in indicated altitude occur when adjusting the altimeter setting?

When adjusting the altimeter setting, an increase in indicated altitude occurs when changing from a lower to a higher altimeter setting. This happens because a lower setting accounts for more atmospheric pressure, which corresponds to a lower altitude. Therefore, when the altimeter is set to a higher setting, it indicates a greater altitude, since the aircraft now references a standard that assumes a higher pressure at sea level.

In practical terms, if a pilot is flying at a certain altitude and switches the altimeter from an atmospheric pressure of 29.00 inches of mercury (inHg), which is relatively low for that area, to a setting of 29.50 inHg, the altimeter will read a higher altitude even though the actual altitude of the aircraft has not changed. This adjustment reflects the aircraft now using a different baseline for atmospheric pressure, indicating it is at a higher altitude than when it was using the lower setting.

Understanding this principle is crucial for pilots to maintain accurate altitude readings, especially in surrounding airspace, where altitude constraints are important for safety and regulatory compliance.