Under what condition will true altitude be lower than indicated altitude when the altimeter is set to 29.92 "Hg?

When the altimeter is set to 29.92 inches of mercury (Hg), true altitude will be lower than indicated altitude in conditions of colder-than-standard temperature. This is because the standard atmosphere model is based on specific temperature and pressure values. Cold air is denser than warm air; thus, when the actual air temperature is colder than the standard atmosphere at a given altitude, the altimeter, calibrated for standard conditions, will read higher than the true altitude.

When flying in colder air, the aircraft will be physically lower in relation to the pressure altitude than the altimeter indicates. The altimeter interprets pressure drops that are typical at higher altitudes, but if the temperature is colder than standard, the aircraft will be at a lower elevation than what the altimeter shows. This discrepancy can create an unsafe situation where a pilot might think they are higher than they really are.

Other conditions such as warmer than standard temperature would result in higher true altitudes, and factors like high humidity or altitude changes like those during a climb would not directly affect the comparison between true and indicated altitudes in this way. Each of these factors influences altitude indications differently; however, the relationship between colder temperatures and true altitude being lower than indicated altitude when set at 29