During which condition should pilots ensure their anti-collision lights are on?

The correct answer is that pilots should ensure their anti-collision lights are on during all operations. Anti-collision lights are a critical safety feature designed to make an aircraft more visible to others, particularly on the ground and in the air. These lights help other pilots, air traffic control, and ground personnel identify and locate the aircraft, especially during high-traffic operations or when performing maneuvers that might not be expected.

Having anti-collision lights on at all times enhances safety by reducing the risk of collisions, particularly in busy environments like airports where multiple aircraft are operating simultaneously. It also serves as a warning to anyone nearby about the aircraft's presence, which is crucial during taxiing, takeoff, and landing phases.

In situations where visibility might be compromised, such as poor weather conditions or night operations, anti-collision lights increase the aircraft’s visibility; however, they are not limited to those conditions alone. Keeping the lights on during all operations ensures consistent visibility regardless of changing conditions or phases of flight.