Which condition increases the danger of altitude errors in colder temperatures?

The condition that increases the danger of altitude errors in colder temperatures is that true altitude is lower than indicated altitude. This phenomenon occurs due to the way altimeters function. Altimeters are calibrated based on the assumption that the temperature of the air is standard (ISA, or International Standard Atmosphere). When the temperature is colder than standard, the air is denser, which causes the altimeter to indicate a higher altitude than the actual true altitude.

As the aircraft ascends in colder temperatures, this discrepancy becomes more pronounced, leading pilots to mistakenly believe they are at a higher altitude than they actually are. This situation can result in hazardous situations, such as obstacles being closer than anticipated or potential terrain impact. Understanding this relationship is vital for flight safety, as pilots must be aware of the temperature effects on their altitude readings, especially in colder environments.