Why do aircraft have landing lights?

I suspect they are to allow a ground observer or possibly another aircraft to locate the airplane. However, I am located under the northeast flyway between New York and Boston and planes are passing overhead day and night. Once when standing in my yard on a moonless night a jet went directly overhead at several thousand feet and the beam actually illuminated the yard for a second. So perhaps they have other uses.

Thank you for the reply, Acquiunk. Maybe they have several uses- if the airport ground lights fail, say. But to me, in this age of automation, they seem a bit of an anachronism.
Anybody else?

I assume that it is no different than cars having daylight running lights. They can be seen better than cars without them. Why should it be any different for a plane?

Another very good answer. For avoiding collisions. Perhaps. But the controller on the ground is supposed to take care of that. I'm beginning to get a belt-and-braces feel to this.

While they do enhance visual identification, they are a comfort to the pilot. Its nice to be able to see just now fast the ground is coming up to greet you.

Apparently, it is also policy with some airlines. Of course, nobody can ever explain policy.

When a plane is approaching for landing, they would be below radar range and a visual from the tower would be required. It would also help ground crews to see the planes more quickly. Some pilots even flash the lights after they have put the flaps and wheels down to alert the tower that they have done so and are coming in.

Good going so far.

Anybody else?

Final bump of the day.

Very good question, McTag! And I like the answers!

I was kind of hoping someone would come up with the definitive international safety code, or something.
They seem to come on about the same time as the wheels are lowered, about ten miles from the airfield.

The lights are not optional when the gear is down for planes with retracting landing gear. One thing they are for is to be able to see any potential obstacles far down the runway, to try and give pilots a chance to go around if say there's a herd of deer on the runway, or a car, person, etc. Not all airports have towers (in fact, most don't), and even then, the tower can make a mistake.

I did not find anything on commercial aircraft, but I just found the following information for light aircraft. This is from the FAA site. It seems to confirm my earlier comments.


Landing lights are not only useful for taxi, takeoffs, and landings, but they also provide a means by which your airplane can be seen by other pilots during flight. FAA has initiated a voluntary pilot safety program. "Operation Lights On" to enhance the "see and be seen" concept of averting collisions both in the air and on the ground, and to reduce bird strikes. All pilots are encouraged to turn on their landing lights when operating within 10 miles of any airport (day and night), in conditions of reduced visibility and in area where flocks of birds may be expected.

Although turning on aircraft lights does enhance the "see and be seen" concept, pilots should not become complacent about keeping a sharp lookout for other aircraft. At times aircraft lights blend in with stars in the sky or the lights of the cities and go unnoticed unless a conscious effort is made to distinguish them from other lights.

Thank you all, honourable mention to Intrepid William, for your helpful and informative comments.

(I was right with the 10 miles! I amaze myself, sometimes)

The landing lights are on primarily so that birds can see the aircraft and get out of the way.

There are many ducks etc flying around airports and many are ingested in the engines.

If the plane survives the engines have to be 'boroscoped' for damage and sometimes replaced.

While the (coloured and white) position lamps are similar to those on ships (110° left; red; 110° right: green; ±70° back: white, left & right.) the airplanes have additionally two landing light systems:
- Inboard landing lights,
- outboard landing lights (mostly more in the middle of the wings).

Usually the outboard landing lights are only turn end, when the airplane got the allowance to land/start. (They beam parallel to the airplane's axes.)

Originally landing lights were for obstacle avoidance during taxi, takeoff, & landing as already noted by others here. In addition they provide visibility and depth perception to the pilot during the last seconds of a night landing as he 'flares' (reduces power while raising the nose for a soft touchdown). Later, as also noted by others, airports required their use by approaching aircraft once they line up for the final approach, sometimes as much as 10 or so miles from the runway - this both for traffic avoidance and to enable the tower operators to identify aircraft in the landing pattern.

Carrier aircraft don't flare on landing - that is they fly a constant angle of attack approach at relatively lower speed with the nose high in the final touchdown attitude - all the way down. Landing lights are not used precisely to prevent the pilot from "spotting the deck". The reason for this is the complete absence of background light to support peripheral vision and depth perception at sea, and the danger that, as a result, the pilot would descend too low and crash into the stern of the ship. Instead he keeps his eyes on an optical glide slope system and is surprised (and often relieved) at the moment of touchdown.

Which reminds me of my naval experiences on a minesweeper:

when in 'war-time-exercise', we didn't light up our position lamps.
However, the outsite control lamps (actually nearly as wide shining as the position lamps) blinked while showing that we were searching electro-magnetical.
If fisherboats came too close, we just used these lamps (without doing any search; besides, that those surges didn't do any harm to anyone and anything besides actiwaiting the counter in the mines ):wink:

While watching movements at Edinburgh,Scotland and listening in on ATC chatter,I notice that the pilots generally turn on the landing lights immediately after recieving landing clearance from the tower. the landing lights therefore act as a warning to any aircraft in the area that the plane is about to land, while also allowing ATC to easily identify the ac and watch its approach.

Landing lights are more for visual identification from other aircraft and the tower than for the pilots benefit when landing.

Additionally, the "Dam busters" used a system of lights to indicate the correct altitude for dropping the bombs: a light on either wing was shone at a certain angle, once the beams merged to a single spot,the aircraft was at the right altitude to drop the bomb.

Not quite true. Both reasons are necessary and sufficient for the use of landing lights. One cannot safely "flare" in close for a soft touchdown (as is the practice in commercial aviation) without the use of landing lights.

An approach without a "flare", using the constant attitude technique used by Naval aviators on aircraft carriers yields precise control of the touchdown point, but at the expense of a decidedly hard landing. Without landing lights, this would be the only safe approach.