Airport codes?

Dana

Dana

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Dana
I've been wondering about the logic behind airport identifiers. Not the ICAO ones which [mostly] are logical, i.e. JFK, HFD, STL, etc. (fun fact: ORD is because it used to be Orchard Field before it was O'Hare), but the little ones with alphanumeric codes. Most of the fields in my area have an "N" or "B", i.e. 42B, N72, N04 (sadly closed), etc., but there are a few "I" codes (1I1) and a smattering of other letters as well. Farther west I see lots of K's (but Cooperstown in NY is K23), O's, and other letters, so it's sorta geographical, but there's lots of overlap. So what is or was the rationale?
 
In Florida it’s Xnn
 
I thought there was a rhyme or reason, might be somewhat regional. Michigan has all the current 6Y_ identifiers. Then again 9D_ has airports in SD, MI, PA.

Crapshoot?
 
Reminds me of a story I heard about area codes on the old Bell Telephone system (not sure if it’s true, but it makes sense). In order to understand how it works, you have to think back to the old rotary dial telephone in the late 1940s, where the smaller the individual digit, the faster the dial returned to neutral so you could input another digit. On those units dialing an 8 or 9 took a long time compared to dialing a 1 or 2. Zero took a seeming eternity.

Thus, the largest, most populous and most politically powerful cities at the time got the best numbers. For example NYC is 212, Chicago is 312, while Lubbock, TX is 806.

Again, not sure it’s true, but it sort of makes sense.
 
Kynadog said:
Reminds me of a story I heard about area codes on the old Bell Telephone system (not sure if it’s true, but it makes sense). In order to understand how it works, you have to think back to the old rotary dial telephone in the late 1940s, where the smaller the individual digit, the faster the dial returned to neutral so you could input another digit. On those units dialing an 8 or 9 took a long time compared to dialing a 1 or 2. Zero took a seeming eternity.
Thus, the largest, most populous and most politically powerful cities at the time got the best numbers. For example NYC is 212, Chicago is 312, while Lubbock, TX is 806.
Again, not sure it’s true, but it sort of makes sense.
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You're version is sort of on track but factually lacking.

The reason for the code assignments was to reduce the load on the mechanical relays at the switches. Thus the most POPULOUS areas got the low numbers, nothing to do with political power. If you look at the earliest area code maps you'll find they reflect the population density map of the time to a tee.

In the mechanical relay era the center digit of an area code could only be 1 or 0. When all switches, and company PBX's switched to digital the magic of that position in the area code went away. That conversion ended in the late 80's, IIRC.

Another interesting "why is it that way" is the Zip code layout. It starts with Zero on the East codes and works it way to 9 on West coast.

Not sure why the National Highway system started with 1 on the West Coast for North-South interstates and 10-90 starts at the Southern boarder for the East-West routes.

Gotta start somewhere I guess.
 
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Back when the telephone system was swiftly expanding, Seattle was "The most electrified city in the US." (Thank God for James D. Ross and his Skagit River hydroelectric vision). I guess that is why we got a 206 code, despite being located far from the greatly more populous east coast.
 
Kynadog said:
Reminds me of a story I heard about area codes on the old Bell Telephone system (not sure if it’s true, but it makes sense). In order to understand how it works, you have to think back to the old rotary dial telephone in the late 1940s, where the smaller the individual digit, the faster the dial returned to neutral so you could input another digit. On those units dialing an 8 or 9 took a long time compared to dialing a 1 or 2. Zero took a seeming eternity.

Thus, the largest, most populous and most politically powerful cities at the time got the best numbers. For example NYC is 212, Chicago is 312, while Lubbock, TX is 806.

Again, not sure it’s true, but it sort of makes sense.
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Your first paragraph made perfect sense, but area codes weren’t required until about the time of tone dial.

Edit: I researched a little and I’m wrong. That said, area codes weren’t dialable until about the time of tone phones. You gave it to the operator for a long distance call before that period.
 
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MBDiagMan said:
Your first paragraph made perfect sense, but area codes weren’t required until about the time of tone dial.
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I think you're misremembering here. 7-digit dialing was the norm well into to 90's. Now 10-digit dialing is required. Prior to the change a Long distance call required a 1 to indicate it was going to be LD, the area code (714), the branch (528), and the exchange (1262). [Don't dial that number, it was my family's number until I was 20. Not sure who has it now]

Now with digital switching and nearly universal "free" long distance, everyone is on 10 digit. With the exception of international calling other than Canada and Mexico which uses 0 (international), 91 (country code, in this case India) and then the correct combination of digits for the destination country.

@denverpilot can probably give us a TL;DR on this topic. :)
 
MBDiagMan said:
Your first paragraph made perfect sense, but area codes weren’t required until about the time of tone dial.

Edit: I researched a little and I’m wrong. That said, area codes weren’t dialable until about the time of tone phones. You gave it to the operator for a long distance call before that period.
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Uh... no. I was dialing long distance before push button phones.
 
Smaller ones by me in Northern Illinois usually have C. C81, 10C, 3CK,06C etc. I really try not to ask the why when it comes to government. Almost always a rabbit hole.
 
MBDiagMan said:
Your first paragraph made perfect sense, but area codes weren’t required until about the time of tone dial.

Edit: I researched a little and I’m wrong. That said, area codes weren’t dialable until about the time of tone phones. You gave it to the operator for a long distance call before that period.
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When I was growing up in the 1960’s and 1970’s and on into the 80’s and 90’s, you had to dial the area code if you made a long distance call to another area code. Not so within the area code, but definitely outside of your own area code.

And, yes, they were dialable on rotary phones. We did it all the time.
 
Ravioli said:
@denverpilot can probably give us a TL;DR on this topic. :)
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There are still plenty of places that’ll do seven digit on POTS.

Examples:

- Pennsylvania’s 814 area code only went to “permissive” 10 digit dialing (meaning either way works while getting people used to it) on Sept 23rd of this year.
- Alaska will switch to ten digit dialing as mandatory in late 2021.
- Same with Florida’s 850 area code. Aug 2021.
- South Carolina 803 did its ten digit dialing overlay in April of this year.
- Hawaii started permissive ten digit dialing in prep for their overlay in Sept of this year. 808 will be joined by 582.

Etc.

Most Voip and PBX providers will let the administrator pick which area code is assumed if only seven digits are dialed, also.

I programmed ours to require ten since we’ve had an overlay since 1999, but when we purchased an Indianapolis office, they weren’t truly used to it. They have an overlay area code but according to them, few have numbers in it.

Our new numbers from our carrier for their direct to desk lines ended up having to be issued in the overlay area code, which surprised them a bit over a year ago. They’d heard of it but found it interesting I couldn’t order numbers in the old area code.

So it’s still very location-dependent. :)

That TL;DR enough?? Ha.
 
The original CAA airport codes were a mix of ones shared with the airline industry (things like ORD, LGA, etc...) and ones that were one letter and two digits (in various order) where the letter corresponded to the overlying ARTCC. For example W66 was an airport in Virginia that was under Washington Center. 1F7 is one in Texas under Fort Worth Center.

A plethora of private airports led the FAA to expand the namespace. Added were four-character codes that used two letters which were the USPS state abbreviation plus two digits like MD50 in Maryland or 5NC5 in North Carolina.

Then ICAO reared its ugly head. ICAO airport codes can't have digits. For the big US airports, this wasn't a problem. You put the US designator K in front of the three-letter code, ORD becomes KORD.
That works in the contiguous 48, but Alaska and Hawaii are in the Pacific zone, so they share codes starting with P with other countries. PHNL is Daniel Inouye (Honolulu) International, PANC is Ted Stevens (Anchorage) International. The US has a good chunk of the P namespace (include PA, PF, PH), but it's shared with Micronesia, Palau, and Kiribati.

Then more ICAO ugliness when we switched to METAR and TAF from SA and FT reports. METAR/TAF requires an ICAO identifier, so there was a rush to rename places that report weather (mostly AWOSs and the like) to have ICAO compliant codes, which is why a lot of places like W66 because KHWY.

Then of course, the FAA decides to just ignore the guidance. W66 and W10 are now in Washington state (go figure). BQ1 is in NC (but does have a good Barbecue restaurant on field, it was 5NC3 before). And, yes they stick illegal things in METARS that begin with K but have digits.

There have been a few renaming of airports that have changed the identifier. Ildewild became JFK when renamed Kennedy Airport. BAL became BWI when it was renamed from Friendship to Baltimore-Washington Internatinoal. Oddly, Denver International usurped Stapleton's DEN id when it opened.
 
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flyingron said:
The US has a good chunk of the P namespace (include PA, PF, PH), but it's shared with Micronesia, Palau, and Kiribati.
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Interesting, I always wondered why Juneau, AK (JNU uses PAJN for it's ICAO code)
 
Ravioli said:
Not sure why the National Highway system started with 1 on the West Coast for North-South interstates and 10-90 starts at the Southern boarder for the East-West routes.
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Which is exactly the opposite of the old US Highway system -- on north-south routes the lowest numbers were in the east and went up as you go west; and on east-west routes the lowest numbers were in the north.
 
Pilawt said:
Which is exactly the opposite of the old US Highway system
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Maybe they needed to stimulate road sign manufacturers and installers.

Also, interstates use a differing thing than state highways, which is another CF to get used to :)
 
Racerx said:
Smaller ones by me in Northern Illinois usually have C. C81, 10C, 3CK,06C etc. I really try not to ask the why when it comes to government. Almost always a rabbit hole.
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It’s because they are (or were) within the bounds of Chicago center. Lots of NorCal (Oakland center) airports have “O” in them. L in SoCal. S near Seattle. Etc. There is some logic to it.
 
My home airport 2NK9. It is in NY. What logic is that? It is a private airport.
 
In the Phoenix area there are 3-character alphanumerics that start with 'P' (makes sense, example P19 Stellar Airpark), 'A' (e.g., A39 Ak-Chin Regional) and 'E' (e.g., E63 Gila Bend Muni).
 
Hmmm, CT is mostly "B", with some "N", two "C", and one "Y". All of the private airports are "CT", with the exception of the Sikorsky factory field (JSD). NY has G, N, A, B, C, E, F, H, I, K, and a few oddballs. The privates are mostly NY or NK, with a few publics NY or NK as well.
 
So that explains why all our county airports here in SW Ohio are I## codes, Indy Center territory.

Nbc_the_more_you_know.jpg
 
Not so sure about that center thing when you look at the airport codes for Michigan.

ZMP, ZAU, ZOB

But we have all sorts of letter/number combos.
 
Not sure of the logic behind airport codes. Our local airport was B24 (AMA Executive), then H30 (Elisha Payne) under new owners, then when the village acquired it and renamed it yet again (Hamilton Municipal) it became VGC, conforming to ICAO (KVGC). But area airports still have legacy names, N03 (Cortland), N66 (Oneonta, now Nader Regional), N23 (Sidney), K23 (Cooperstown), 6B4 (Frankfort-Highland), etc. I'm not sure how we rated a three-letter name, other than we were one of the first small batch of rural airports to get LPV approaches. We wanted HAM or VOH, but they wouldn't give it to us. so we got VGC instead. We decided it stood for "Very Good Community." Outside of the Syracuse area, no one has a clue where VGC is. And if you say Hamilton, you will occasionally get "in Canada?" as a response.
 
Yep, when heading to a small distant airport VFR, I usually have to give a big city. Nobody used to know where VKX was, so I just told people it was ADW. When finally handed off to approach there, they'd ask "Potomac or Hyde." Similarly, nobody knows my little private strip of NC26. I tell ATC I'm going to SVH which usually works. ZTL usually has no problem when I tell them where I'm really going.

Oddly, it all works fine if I file IFR direct to my destination. Well, most of the time. One time they routed me over my destination and I was bearing down on the CLT runways before I prodded them that they'd vectored me past my destination.
 
Three letter airport IDs - tower or onsite navaid, scheduled air service, weather reporting onsite, or Customs.

One letter, two digits - public use small fields.

Two letters, two digits - private fields.

Unless they make an exception, which usually isn’t done unless they do.
 
Note that the above is mostly right except the one letter/two digits say "mostly" with regard to the allocation.
The two letter/two digit codes are supplemental for PRIVATE USE (not necessarily privately owned) fields.
This is all laid out on order 7350.9.
 
ateamer said:
Three letter airport IDs - tower or onsite navaid, scheduled air service, weather reporting onsite, or Customs.

One letter, two digits - public use small fields.

Two letters, two digits - private fields.

Unless they make an exception, which usually isn’t done unless they do.
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Any rhyme or reason to the placement of the letter in the 1+2 codes?

And what’s the deal with KHBC, KBWW, KPHP, etc? Did Phillip, SD, used to run 74’s to Mohall, ND with a layover in Bowman?
 
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