I could have sworn I read an article on this a few years ago, but cannot find it. I'm just curious.

Say I book a ticket from AA and the reservation code is ABCDEF.

Do those letters mean anything? Is there any rhyme or reason to which letters the PNR is assigned, or is it totally random? Any link to geography or POS or type of ticket?

Is this true for both Sabre and Amadeus?

My understanding is that a lot of these systems are based on the same thing - IBM's TPF operating system where is is all about performing fast transactions.

Someone once told me that the locator actually maps/hashes to a disk location on the system. I don't know if that is still the case but I don't doubt it at least in the beginning of these systems. Just think these systems were developed 50+ years ago and memory, disk space, network and processing power were all expensive. So, they had to squeeze every byte and CPU cycle and wrote in assembly language (simple machine instructions).

I know on the UA SHARES system, if I make a few reservations in a row, the locators appear to be in some kind of sequential sorted order.

Please follow the redirect to TravelBuzz.

~beckoa, co-moderator Information Desk

The PNR confirmation codes (Record Locators) are typically a hash algorithm that maps to a particular disk storage loaction (file address). The numbers are random, though there is typically a table of dirty words that is used to compare and exclude the use of "bad words" as record locators.

they probably would, and charge us for it.

many airlines have in house systems that assign their own PNR

Korean Air uses your phone number

and no, PNRs are not random. they are mostly random, but airlines have learnt to censor bad 3-6 letter words that they don't want in PNRs.

It depends per GDS.

Sabre PNR's are completely random (only letters though).
Amadeus and Galileo PNR's are in a certain sequence. Both use letters and numbers.

AA names itns, if I'm flying from JFK to ZRH, it would be JFK/ZRH, for one such trip my PNR was nearly a "permutation" of those letters, from my recollection something like ZHRKJA--I've flown this itn many times, but only that particular itn was even close, so mostly likely only a coincidence.

Some airlines go further with non-randomness. For example Air NZ PNRs always end in "H".

Not mentioned above but an airline shouldn't have more than one current ticket with the same PNR. In practice PNRs are not recycled for a short while in case of any post-travel issues.

I really don't think locators are random. If you think about it, if it is random, then it can repeat, which we know does not happen. I don't think the algorithm would say generate something randomly and then check for duplication, etc.

I would guess in the best case, it would be "random within a set of rules".

Note also that some airlines share the same system and some GDS are also used by airlines for internal reservation processing (e.g. SABRE and AA).

This is a fascinating discussion...while airlines may have algorithms to stop bad words, funny combinations still exist. Cool to know that PNRs can be repeated, but only after some time past the travel date.

How does Korean Air incorporate the phone number though?

I'd like to hear an explanation of that too. I believe the KE system is Amadeus based, since the records I've seen always have airline record numbers that match that gds (if booked in Amadeus).

They certainly aren't completely random, if you make multiple bookings within a short space of time the first two characters are normally the same.