Airlines are running out of 4-digit flight numbers • Hacker News Board

Re: Airlines are running out of 4-digit flight numbers

#251

Post by alexpotato » Mon, Aug 05, 2024, 1:01 PM UTC

Many years ago, I worked on a trading floor.

The legacy trading system (X Windows/Solaris/C++ based) was originally written in a time where market volumes were low so you couldn't have more than 10,000 orders (due to a limit on the size of the order id field).

As volumes increased in the late 2000's, there were days where we were in danger of running out of orders ids.

The fix? The system generated order ids 7 days a week even if trading only happened 5 days so we "borrowed" order ids from Saturday.

Re: Airlines are running out of 4-digit flight numbers

#252

Post by alexpotato » Mon, Aug 05, 2024, 1:06 PM UTC

gentle wrote: post #83

I love that so many people here think they can think about the problem for 10 seconds and come up with a solution that hasn't already been considered a thousand times and discarded.

I think people forget that problems like these have two parts:

- a technical solution that is generally somewhat obvious or at least is picking which of 2 or 3 proposed solution makes the most sense

- a co-ordination problem that will require hundreds of different entities to agree on timelines, rollout plans etc etc

Now, this does happen (Sweden switching traffic side of the road [0] an Y2K) every so often but it's a LOT of work.

0 - https://en.wikipedia.org/wiki/Dagen_H

Re: Airlines are running out of 4-digit flight numbers

#253

Post by Schiendelman » Mon, Aug 05, 2024, 1:08 PM UTC

globular-toast wrote: post #167

lxgr wrote: post #146

Earlier quoted context omitted.

I could imagine many legacy systems identifying “their” flights based on the alphanumeric prefix alone (as opposed to doing a database lookup).

Yep. Not only a ton of software would make this assumption, but a ton of human-based processes too. Lesson: if you make your IDs easily decodable, people will decode them and use them directly instead of whatever API you intended them to use.

That's what happens with requisition numbers for jobs! If they're too short (12345), recruiters remember them, start building manual processes dependent on them, and then when they collide with others on a job board (like Indeed, or if the employer hires an agency to help) you end up needing a parallel identifier...

Re: Airlines are running out of 4-digit flight numbers

#254

Post by delfinom » Mon, Aug 05, 2024, 1:15 PM UTC

ginko wrote: post #171

zeagle wrote: post #80

Clearly the successor solution is to use eight groups of four hexadecimal digits each, separated by colons. Then each individual seat and peanut could be addressed to it's final destination. More seriously the solution suggested of giving the 3 companies other unused prefixes like D* U* and A* to use with their codeshares and non rev flights to start seems the easiest.

Why do airlines even need separate flight numbers for codeshare flights? Why not just use the flight number of the operating airline in the booking? IMO it's just confusing for passengers as well.

The marketing carrier, aka the one with the airline code on the ticket becomes liable for certain things in most countries. Codeshare is one way who is responsible is known to outside parties immediately. It also impacts automatic luggage transfers for layovers.

Not to mention, there are bits where if I buy a JAL ticket for AA internationally, I get 2 free checked bags while the same AA sold and operated flight has no free checked bags. The JAL code lets the airline systems quickly determine they can't force you to pay up at the luggage drop-off because you are under the other carrier's rules for the flights.

A lot of this is based on the pre-smartphone age but I don't think there's better solutions that are both computer, person and policy friendly either.

Re: Airlines are running out of 4-digit flight numbers

#255

Post by regular_trash » Mon, Aug 05, 2024, 1:15 PM UTC

snapcaster wrote: post #228

jll29 wrote: post #227

> Here’s the full answer, along with how they triage the problem – for instance by assigning the same flight number to more than one flight a day (although that means they need for it to be flights that would never both be in the air at the same time, such as where the same plane is used and can’t reasonably be substituted) This sounds like it's calling for trouble! Whenever I hear that any IDs could be "recycled", I…

>Whenever I hear that any IDs could be "recycled", I make a mental note to replace the person making such a proposal from all teams that I am involved in. Couldn't agree more, not even interested in debating it

The misconception here is that Flight numbers are not treated as IDs. A unique key to any flight is the composite of number/origin/departure date.

And it's mostly a holdover from legacy systems airlines are entrenched in, so there isn't much else anyone can do here short of completely reinventing the mainframe reservation systems and heavily refactoring all the pieces that depend on it.

Re: Airlines are running out of 4-digit flight numbers

#256

Post by vel0city » Mon, Aug 05, 2024, 1:18 PM UTC

cobbzilla wrote: post #247

jll29 wrote: post #227

> Here’s the full answer, along with how they triage the problem – for instance by assigning the same flight number to more than one flight a day (although that means they need for it to be flights that would never both be in the air at the same time, such as where the same plane is used and can’t reasonably be substituted) This sounds like it's calling for trouble! Whenever I hear that any IDs could be "recycled", I…

Have you ever changed the static IP address of a computer? You just “recycled” a “globally unique” ID. Recycling unique IDs (more precisely: changing the underlying thing the ID points to) is not impossible; there’s lots of pathological failure modes; for certain ID-spaces it’s kinda a required use case; so we have to deal with it.

IP addresses (especially IPv4) are not even supposed to be globally unique.

How many 192.168.1.1 devices are out there? How many different distinct physical boxes respond to traffic going to 1.1.1.1?

Re: Airlines are running out of 4-digit flight numbers

#257

Post by xhkkffbf » Mon, Aug 05, 2024, 1:19 PM UTC

jll29 wrote: post #227

> Here’s the full answer, along with how they triage the problem – for instance by assigning the same flight number to more than one flight a day (although that means they need for it to be flights that would never both be in the air at the same time, such as where the same plane is used and can’t reasonably be substituted) This sounds like it's calling for trouble! Whenever I hear that any IDs could be "recycled", I…

Isn't this what Southwest essentially does? I've been on a Southwest flight that makes four or five stops, all with the same number. But I'm sure no person took more than one stop on the same plane.

Re: Airlines are running out of 4-digit flight numbers

#258

Post by rhplus » Mon, Aug 05, 2024, 1:27 PM UTC

JCharante wrote: post #222

gentle wrote: post #83

I love that so many people here think they can think about the problem for 10 seconds and come up with a solution that hasn't already been considered a thousand times and discarded.

My solution: Stop codesharing with marketing flight numbers that are useless. Airlines do perfectly fine selling tickets without having the flight marketed by themselves and they can handle inter-airline agreements without it.

Customer behavior is key here. There’s perceived risk with the dreaded “Multiple airlines” option when booking tickets, especially for international flights. No-one wants to find out the hard way that there weren’t agreements or reciprocal status or matching luggage allowances, etc. The code-share is shorthand for “we’re responsible”.

Re: Airlines are running out of 4-digit flight numbers

#259

Post by ryukoposting » Mon, Aug 05, 2024, 1:27 PM UTC

jll29 wrote: post #227

> Here’s the full answer, along with how they triage the problem – for instance by assigning the same flight number to more than one flight a day (although that means they need for it to be flights that would never both be in the air at the same time, such as where the same plane is used and can’t reasonably be substituted) This sounds like it's calling for trouble! Whenever I hear that any IDs could be "recycled", I…

I'm certain each flight has its own completely unique ID buried somewhere in a database. But, shorter codes can be spoken into a radio faster and with lower probability of misinterpretation - both critical features for air traffic control.

Those shorter codes will necessarily be reused, it's just a question of the time interval between re-uses of any particular code.

I faintly recall seeing two Southwest flights from ORD to BWI that had the same code a couple years ago, so I decided to look it up. And yes, it's a thing: Flight 1555 from ORD to BWI departs at 4PM today, and flight 1555 from ORD to BWI departs at 4:20PM tomorrow.

I'm curious, can anyone find a re-used code on a shorter time interval than that? It seems like 24 hours is perfectly reasonable, but how narrow can the window be? 12 hours? 6?

Re: Airlines are running out of 4-digit flight numbers

#260

Post by madeofpalk » Mon, Aug 05, 2024, 1:30 PM UTC

jll29 wrote: post #227

> Here’s the full answer, along with how they triage the problem – for instance by assigning the same flight number to more than one flight a day (although that means they need for it to be flights that would never both be in the air at the same time, such as where the same plane is used and can’t reasonably be substituted) This sounds like it's calling for trouble! Whenever I hear that any IDs could be "recycled", I…

> although that means they need for it to be flights that would never both be in the air at the same time

It's interesting that this is called out, because there are frequently at multiple flights in the air with the same flight number

QF1 / QF2 is now over 24 hours, and has daily flights. It seems pretty feasible to have the SIN-LHR leg be delayed just enough so there's two SIN-LHR QF1s in the air at the same time.

Singapore Airlines has some 19 hour flights. Qantas hopes to have a 22 hour flight 'soon'. Very feasible that these can be delayed just long enough so there's two of the flights in the air at the same time.