[phil21]

From what I know... Not affiliated at all with the airline industry, but I fly a lot and tend to nerd out on this stuff...

Their crew (and flight) scheduling software functions in a manner where it more or less simulates a "perfect" day of operations. Airplanes take off on time, land, and continue on. If anything disrupts this simulation, crew members had to call in and talk to someone to update the computer system to tell it that both the airplane and crew members are not where the system thought they were.

Once the call center got overwhelmed it was a cascading failure with Southwest quickly not understanding where most of their flight crew happened to be at any given moment. It appears they feel the only way to solve this is get everything (planes and crews) back into "starting position" to restart the simulation.

[Simon_O_Rourke]

In this age of more or less fully network connected devices, this kind of a setup seems archaic in the extreme, probably likely to be some hangover from the 70s or 80s.

[pavlov]

Airline systems are some of the oldest computing architectures in use.

The Sabre reservation system was created by IBM for American Airlines in the 1950s — when a computer filled an entire building floor and was built out of vacuum tubes — and remains actively used today by multiple airlines. The programming language has been switched several times over the past 60+ years, but essential compatibility remains.

[persona_reuse]

I can't remember where I read this and I can't find a cite right away, but I bet someone can confirm-or-correct me: the 6-letter reservation code for your flight? That used to be an explicit pointer of memory in oldold Sabre.

[tracerbulletx]

The IBM 1301 disk manual (A22-6785), for the 7090 computer that SABRE was first used with seems to have a record address scheme that matches.(see page 10, Record Address) http://bitsavers.org/pdf/ibm/7090/A22-6785_1301_1302_on_709x...

[rtev]

I really hope that’s true, it’s hilarious either way!

[ethbr0]

Indeed. Probably the only equally complex and old dynamic computing systems out there are railroad and federal economic ones.

[logosmonkey]

Apparently Southwest is one of the biggest offenders in the airline industry when it comes to not investing in their IT infrastructure. You can only get away with that sort of debt for so long.

[jeffwask]

I knew someone who was working on this, my understanding was technology infrastructure was a huge blocker to their plans for international flights. The scheduling system required many hours of downtime every night to process. It effectively ran from the moment the last airport on the west coast closed to start of operations next day east coast and it was just getting longer.

[Simon_O_Rourke]

If that's true, and I have no reason to doubt it, the blame will fall squarely on the team who were asking for IT investment, and not the leadership who said no to them.

[thisisbrians]

If IT is smart, there will be a paper trail to prove these asks were made/denied.

[widowlark]

So accurate, it just happened:

https://www.theregister.com/2022/12/28/southwest_outdated_it...

[mikewarot]

>You can only get away with that sort of debt for so long.

Kevlin Henney has recently suggested we should stop calling it technical debt, and start calling it technical neglect instead.

Managed debt is a useful thing, if you ignore debt, you end up out of business.

[esaym]

I have a relative that worked in the IT department at SW. Can't remember the details but he said some main parts of their scheduling software were written in the 60's (or maybe even 50's). And it is still running.

Edit: Ok reading comments jogged my memory. It was something to do with the 'Sabre' system which was from the 1950's.

[readthenotes1]

This is true but also true for AA and several other airlines, for reservations and more but not crew scheduling. Sabre is old, huge, and complicated, but is not at fault here.

They run on a specialized version of Sabre that doesn't work the same as the other airlines on Sabre (AA, etc.) which is one reason you don't get SWA flights in Orbitz, etc.

[markus_zhang]

Maybe it evens runs on some mainframe systems since the 80s.

[HDThoreaun]

The airline industry is one of the most competitive in the country. You succeed by ruthlessly cutting costs and offering tickets for $5 less than your competitors. And that’s how we end up with software from the 80s

[twobitshifter]

I’m not sure that’s the case although we heard that third hand from Reddit.

https://blog.geaerospace.com/technology/big-wins-in-flight-e...

Skysolver is a GE Flight Services trademark - there’s a video here showing how it works and SW planes in the video. Contrary to the reddit claim, it does appear to use a predictive algorithm.

Highlight quote from the video: “It is humanly impossible when there’s a major disruption for somebody to figure out what the optimal approach is to get them back on schedule”

Edit: I could see tracking off-duty crew being difficult and done by phone - employees don’t carry beacons and would you want that surveillance from your company? In this situation many crew could be home for the holidays and far from their last known location, and stranded due to problems with other airlines, trains, or roads.