Exterior aircraft lights serve several purposes, but the bottom line is that, in both day and night conditions, lights increase safety and reduce the chance of collisions.
The types of exterior lights that are common on most aircraft are position lights, anticollision lights, and landing/taxiway lights. They help pilots see other aircraft in the air and on the ground and determine their position relative to those aircraft; illuminate ground surfaces such as taxiways and runways; and can even indicate when an aircraft is running.
Anticollision lights are the blinking red and/or white lights commonly found on the top and bottom of the airplane and on the wingtips (the strobes). These are required for night flights yet also are a helpful safety tool in daylight.
The rotating beacon light found on the top of the aircraft’s tail is turned on as part of the engine start checklist. The beacon, along with the pilot’s verbal “clear” warning, alerts anyone nearby that the engine is running, or soon will be.
Landing lights are turned on during descent to an airport and kept on throughout the landing. Be aware that, while this increases visibility, there are illusions associated with having the landing light on during descent. It makes the lighted area appear higher than the non-lighted area, which could potentially lead to a higher-than-normal approach and ultimately a hard landing.
Pilots have some discretion (aside from night flying requirements) about when to use lighting, which can cause differences of opinion. Some pilots prefer to turn off exterior lights when not required, to preserve the life of the bulbs. Others prefer to leave all exterior lights on—even the landing light—throughout each of their flights regardless of conditions to make their aircraft more visible to other pilots. Discuss the pros and cons with your flight instructor—who may recommend leaving the lights on, especially when maneuvering in the practice area.