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I had thought that someone such as ICAO was coordinating the assignment of five-letter waypoint names such that they were globally unique.

Now I notice that OpenNav knows three different waypoints named PINTO, two of which are on the same continent.

Is this supposed to happen? Are there rules for how close identically-named waypoints can be to each other?

(A significant factor in the AA 965 crash was that there were two NDBs with the same ID close to each other, and the FMC selected the wrong one to fly towards. This might be inevitable when NDBs usually have one- or two-letter IDs, but surely with a big fat five-letter namespace uniqueness ought to be achievable?)

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    $\begingroup$ Related: How are airspace fixes named? $\endgroup$
    – fooot
    Feb 19, 2015 at 15:14
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    $\begingroup$ @HenningMakholm Not a problem. I removed the word unique because there cannot be levels to uniqueness. E.g. something cannot be 10% unique or 58% unique. $\endgroup$
    – Farhan ♦
    Feb 19, 2015 at 16:58
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    $\begingroup$ @Farhan: But something can be "globally unique" or "unique within a hemisphere/continent/1000 nm distance", or some other quantified amount of uniqueness. $\endgroup$
    – hmakholm left over Monica
    Feb 19, 2015 at 17:00
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    $\begingroup$ You might enjoy this $\endgroup$
    – Simon
    Feb 19, 2015 at 21:41
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    $\begingroup$ @birdus: So what is your response to my explanation of how something can indeed be more or less unique? $\endgroup$
    – hmakholm left over Monica
    Mar 25, 2015 at 19:48

3 Answers 3

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The names are not globally unique and when entering the plan into the FMC, the crew should check the leg distance. They are sufficiently far enough that the crew will see 1,812 miles instead of 135 miles.

Many FMCs will also only offer "sensible" choices and a deliberate action is required to select a "nonsensical" waypoint.

Often, a mistake in choosing the wrong waypoint will also alert them with a "not enough fuel" message, or an obvious gross error such as a total distance of 3,323 miles instead of the 756 miles expected.

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  • $\begingroup$ So, a waypoint name along with its distance makes its unique. $\endgroup$
    – Farhan ♦
    Feb 19, 2015 at 16:59
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    $\begingroup$ Unfortunately, according to the Wiki article about flight AA965 that was linked in the question, it sounds like R was used for both the ROMEO and ROZO NDBs in Columbia. Since Columbia is only but so big, and these pilots were in a pressure situation, they failed to note the difference. $\endgroup$
    – FreeMan
    Feb 19, 2015 at 17:22
  • $\begingroup$ @Farhan not if you're equidistant from the waypoints! $\endgroup$
    – rbp
    Feb 19, 2015 at 17:59
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    $\begingroup$ @J...: The point is that -- if these answers can be trusted -- there seems to be no rules (or even loose guidelines or rough statements of intent) for what "the half-distance between same-named fixes" can be, so how can you make sure of that? $\endgroup$
    – hmakholm left over Monica
    Feb 20, 2015 at 10:26
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    $\begingroup$ @HenningMakholm I'm not sure if that's a rhetorical question. I guess the only way to be sure would be to run the data through analysis and check. If there are any examples you can find where a real flight path would encounter ambiguity between two waypoints with the same name it would be interesting to see it. If you consider the longest leg between waypoints on any flight plan, it's not going to be a very large distance. Within that radius, I'm not sure you'd find two same-named waypoints anywhere. $\endgroup$
    – J...
    Feb 20, 2015 at 11:26
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Each country's aviation authority is responsible for naming their own waypoints, so it's up to them how far they try to avoid duplication. In the US, the FAA's Procedures for Handling Airspace Matters section 3-3-4 simply says:

e. AIM [Aeronautical Information Management] must not duplicate any radio fix, waypoint, marker beacons or compass locators names.

So they are (or should be) unique within the US, but they aren't guaranteed to be unique globally, although presumably other countries also have policies to avoid duplicate names. For example, this answer quotes similar language from the UK's CAA and has some additional information.

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    $\begingroup$ So if country A and country B both decide to define MYPNT a few kilometers from each other across their mutual border, neither of them will have done anything wrong? $\endgroup$
    – hmakholm left over Monica
    Feb 19, 2015 at 22:32
  • $\begingroup$ @HenningMakholm No. But they just wouldn't do that. Just because the law doesn't prevent it doesn't make it right or sensible! $\endgroup$
    – Simon
    Feb 19, 2015 at 23:47
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    $\begingroup$ @HenningMakholm They won't have done anything illegal, but they will have done something stupid and potentially dangerous. I can't find any documents on it, but I guess that most national aviation authorities are smart enough to avoid doing that, and it's even possible that there's some kind of international co-operation on naming between individual countries. In Europe ATC (Eurocontrol) is kind of international anyway, so there's probably some coordination there at least. $\endgroup$
    – Pondlife
    Feb 20, 2015 at 14:06
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According to ICAO document Annex 11 — Air Traffic Services; Appendix 2:

2. Designators for significant points marked by the site of a radio navigation aid

(...)

2.1.2 In selecting a name for the significant point, care shall be taken to ensure that the following conditions are met:

a) the name shall not create difficulties in pronunciation for pilots or ATS personnel when speaking in the language used in ATS communications. Where the name of a geographical location in the national language selected for designating a significant point gives rise to difficulties in pronunciation, an abbreviated or contracted version of this name, which retains as much of its geographical significance as possible, shall be selected;

Example: FUERSTENFELDBRUCK = FURSTY

b) the name shall be easily recognizable in voice communications and shall be free of ambiguity with those of other significant points in the same general area. In addition, the name shall not create confusion with respect to other communications exchanged between air traffic services and pilots;

(...)

3 Designators for significant points not marked by the site of a radio navigation aid

3.1 Where a significant point is required at a position not marked by the site of a radio navigation aid, the significant point shall be designated by a unique five-letter pronounceable “name-code”. This name-code designator then serves as the name as well as the coded designator of the significant point.

3.2 This name-code designator shall be selected so as to avoid any difficulties in pronunciation by pilots or ATS personnel when speaking in the language used in ATS communications.

Examples: ADOLA, KODAP

3.3 The name-code designator shall be easily recognizable in voice communications and shall be free of ambiguity with those used for other significant points in the same general area.

3.4 The name-code designator assigned to a significant point shall not be assigned to any other significant point.

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