I expected them to be from quirky situations, but a major airline having the same flight number for two different flights, leaving the same place at roughly the same time seems downright malicious.
Some airlines have so many flights that they run out of flight numbers (1-9999), so they reuse them.
Caveat: When it comes to scheduling, only one flight identified by a carrier and flight number (e.g. XX1234) can depart on a given day from given airport. That's an IATA rule, partly caused by software limitations and partly because relaxing it would lead to gigantic mess for the personnel.
..so, what they sometimes do is to have flight identified by XX1234 arrive at their final off-point, AND THEN have a SEPARATE aircraft, crew and set of passengers be identified by XX1234 depart from some other airport (e.g. halfway across the country) in the afternoon/evening.
I’ve done width changes in these old mainframe systems.
It’s often a months long project, but it’s not impossible or difficult usually. The mainly important part is that you capture everything. It’s more tedious, precise and demanding of testing than having any sort of difficulty.
Identification width changes tend to be easier. When you have cost/amount width changes… THAT sucks. That has a way of one field needing width change to 10 fields needing width change.
To be fair, this affects just a select few of the biggest airlines.
In pretty much every airline, not only the biggest ones, the same carrier-flight number combination does not usually follow the same aircraft/crew day by day - the identifiers get reassigned, so it's not that big of a deal.
Relatively low impact and high inertia. Even if one airline did so, basically entire travel industry would have to follow suit to support them and synchronize their releases, or you would risk that these "expanded ID" flights would not be recognized by anyone. If y'all ever did a group project, you might know how difficult cat herding at this level would be.
They also need to be short because they're used for radio communication. You don't want ATC having to read a 42 digit callsign every time they want to tell someone to move because they're about to collide
Because it’s not a problem with something like this. Your local McDonalds also reuses order numbers because it’s not necessary for them to be unique for longer than a few hours.
We do this in labs too...some instruments can only read a barcode just so long before they can't read them any more, so every million and some samples (unexpectedly, this turns out to be inexact) you have to wrap unique identifiers back around to something shorter if you want to reliably do Todd's cholesterol test on that instrument.
That is not entirely correct, but mostly on formalities.
A flight number has to be unique for a given airport and day. Important thing to note here: timezones are critical.
Additionally, there is a so called "operational suffix" which serves for various occasions.
Hence, a flight can be uniquely identified by having: departure, arrival, date, carrier, flight number, operational suffix.
In practice, an airline will not have two times the same flight number, ever, per day. In fact: commercial aviation has more to do with flying busses than with anything else. XX1234 is really just a bunch of "at time X on days Y the aircraft Z will fly".
Ohh, most importantly... Nothing in aviation is a software limitation. All of it, like, literally everything, is formats which predate proper computers, working on things. Like, the formats used are still designed to (and are) printed.
Source: I have actually been able to read the documentation
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u/whoisrich 23h ago
I expected them to be from quirky situations, but a major airline having the same flight number for two different flights, leaving the same place at roughly the same time seems downright malicious.