While only Runway Lights (RL) will be sufficient at night for the aircraft to take off, both RL and Runway Centre Line Markings (RCLM) are required to take off during the day. Isn't it illogical? The image is taken from the low visibility take-off section of the 10-9 page Jeppesen chart of Tekirdağ Çorlu Airport (LTBU).

Part of Jeppesen chart 10-9 showing take-off requirement for various visibility conditions

  • 4
    $\begingroup$ For those of us unfamiliar with the acronyms, the question is referring to Runway Lights and Runway Centre Line Markers. $\endgroup$ Commented Feb 11, 2023 at 4:17

1 Answer 1


To me it makes perfect sense if you consider that at night there is high contrast between darkness and the lights. It is easy to make out the runway edge lights through the fog under darkness, so the lateral position of the aircraft on the runway and its alignment with the runway can be estimated from lights only.

Under daylight conditions the fog itself is scattering the sunlight. The contrast between the runway lights and the scatter is much lower, preventing the pilots seeing lights further down the runway. Therefore during daylight, the runway's center line markers are required so that pilots can see the lateral position and alignment with the runway.

Landing in fog: day versus night Image sources: Day landing and night landing

These images show how much more pronounced the edge lights are at night compared to during daytime.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .