What happens to the windshield heat when flying at altitude regardless of temperature?

The correct choice indicates that the windshield heat remains ON when flying at altitude, which is important for maintaining visibility and safety. At high altitudes, temperatures can drop significantly, even if external flight conditions might suggest otherwise. The windshield heat is designed to counteract ice and fog formation on the windscreen, which can occur due to the combination of low temperatures and moisture in the air.

By keeping the windshield heating system active, pilots ensure that visibility is preserved, thus allowing for better control of the aircraft and safer operations. This function is essential in preventing icing that could obstruct the pilot's view or affect the aircraft's aerodynamic performance. Hence, the system is engineered to operate continuously at altitude as a precautionary measure.

Other choices do not account for the need to maintain effective windshield heating at altitude, which is critical for safe flying conditions.