Which light helps distinguish a plane's direction of travel?

The navigation lights are specifically designed to help distinguish a plane’s direction of travel in the air and during ground operations. These lights, which typically include red lights on the left wingtip, green lights on the right wingtip, and a white light on the tail, allow other pilots and observers to determine the aircraft's orientation and heading.

When viewed from the front, a conventional aircraft will show a green light on the right side and a red light on the left, indicating to oncoming traffic which way the aircraft is facing and moving. This is critical for avoiding midair collisions, helping pilots maintain safe distances and awareness of other aircraft in their vicinity.

Other lighting options like landing lights, taxiway lights, and strobe lights serve different purposes. Landing lights are primarily for illuminating the runway during approach and landing; taxiway lights aid in ground navigation and are designed to guide pilots along taxiways, and strobe lights are used to increase visibility during flight, particularly in low-light or adverse weather conditions, but do not indicate the direction of travel. Thus, navigation lights are the correct answer as they directly contribute to identifying the flight direction of an aircraft.