Los Angeles International Airport (KLAX), for example, has four parallel runways. Since there are only three designators for parallel runways (L, R, and C), two runways are offset by one unit (i.e., 6L/R, 7L/R, 24L/R, and 25L/R). To preserve the runways' actual headings, could airports/aviation authorities adopt terminologies such as "port" and "starboard" for pairs of parallel runways? In this example, there would be runways 7P/S, 7L/R, 25P/S, and 25L/R.

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    $\begingroup$ It is an interesting question. The idea of offsetting the number for more than three parallel numbers also is true for multiple airports in an area with "parallel" runways. Consider KDMA and KTUS. They are 4NM miles apart and the runways are on a magnetic heading of 123°. KDMA has a 12/30 runway assignment while KTUS has a 11/29 L/R assignment. Interestingly, this is documented in the US TERPS. $\endgroup$
    – wbeard52
    Oct 9, 2022 at 13:56

1 Answer 1


The current system of grouping parallel runways in sets of three at maximum is the simplest and most comprehensible way to designate runways.

TL;DR The accurate correlation of runway numbers and their actual headings is of little importance, even more so when compared to the necessity of avoiding confusion.

Left - Center - Right leaves pretty much no chance for error(*, and is adequate for the vast majority of cases.

More in depth: As for the number part: all pilots know that runways are numbered according to their magnetic heading, which is rounded to the nesrest ten and then truncated. Since the magnetic poles move, it may very well be that the actual runway heading has changed over time such that a runway 21 may actually have a heading of 217. Because of this, pilots are not expecting the number to match the heading with great acuracy.

So: "runway 21 right" is very simple, efficient and clear way to designate a runway the heading of which is about 210 degrees and which is to the right of a parallel runway. In the case of four or more parallel runways (KORD has six), it is equally efficient and clear to divide them into two groups. Having four, let alone six, parallel runways with the same number, but more letters to name them would only add the chance of confusion.

The current system has the benefit of subsequent numbers being clearly distingquishable phonetically. There is very little chance of mixing up, seven with six, for example.

And as a final note: the current system is also distinct from other phraseology used in airports / -fields. The taxiways are named with letters, so using that option for runways would add the risk of miscommunication.

  • people with difficulties distinguishing left and right will not end up as pilots or air traffic controller.
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    $\begingroup$ Furthermore, consider this: How many airports are there with more than three parallel runways? (10 with more than three, 3 with more than four, none with more than five) How many of those are within the same jurisdiction? (The FAA has the most with 7) How much trouble would it be to invent a new convention only for those 7 airports? $\endgroup$ Oct 9, 2022 at 10:59
  • $\begingroup$ Chicago O'Hare has 8 rwys, 6 of which are parallel. Not sure though if all of them are currently operational. Just sat on a plane there that was part of a three parallel approach flock 🙂 $\endgroup$
    – Jpe61
    Oct 9, 2022 at 13:51

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