As you said, this is certainly a complicated situation.
But this is HN, and, from an optimization / constraint satisfaction problem perspective / scale perspective, it’s really not a very large problem. The “going home” problem is a standard programming contest problem. This is more constrained, but a globally optimal solution isn’t needed. Southwest literally has a program called SkySolver. It should work.
So you need to choose destinations for a few thousand planes? Pick the place you would normally have them at 4 AM two days hence. Need captains familiar with the airports? Surely the captains who would normally fly from a given airport at 4 AM two days hence are familiar with those airports. This gives a good starting solution for further optimization.
You need to get a message to ~20k people? Great, Twilio will do that with minimal effort.
Will a budget of a couple million dollars, this is not hard. There are good SMT solvers available for free. CPLEX is expensive but not on this scale. Managing test cases on this scale is straightforward.
Even in an emergency, something good enough to get to the point where SkySolver starts working again should be doable.
People who manage electric grids have protocols for “black starts”. These protocols are messy and complicated, but they are developed in advance, and they work. Airlines should have the equivalent capability.
> But this is HN, and, from an optimization / constraint satisfaction problem perspective / scale perspective, it’s really not a very large problem.
i can't even begin to imagine what the utility function _alone_ must look like.
the solver can't just produce a blank slate solution every time, it's got to optimize... something, subject to some constraints about not changing too much from the previous plan it came up with. and it's probably got to do this every time there's new real world input.
> The “going home” problem is a standard programming contest problem.
the hubris and handwaving on here is hitting epic levels.
You touched upon the core issues. Yes, SkySolver should be able to get a solution quickly. Yes, there should be systems in place to co-ordinate invidividual actions of 20k people with rapid adjustments. Yes, they should have procedures in place to do "black starts". But they don't. And you can't design, test, and roll out even a new communications system to 20k users literally overnight. If they existing scheduling system doesn't already email crew, then do they have email addresses for all them? If so, it's probably in HR somewhere; if that's outsourced then it could take days for SWA to get that pulled out even on an expedited basis. If they send email, what percentage of crew will receive it? In what timeframe? Email campaigns are notoriously porous. And how do crewmembers provide feedback? A standalone web page? Great--how do you authenticate? By interfacing the existing system? What will that take? Probably not, though--it appears the existing feedback mechanism is a manual phone call to a person. Do crewmembers even have login IDs?
Finally, even with perfect communication there's the problem of getting people where they need to be when the transport system is very flaky. I think that's probably the issue when the CEO said 'they would get things manually set up, and then something would happen and we'd have to start all over again.'
The pilot's union and others have been critizing SWA for not investing in infrastructure. The previous CEO, responding to the previous melt-down, said something about 'you can't test for these kind of scenarios.' That's wrong. You can't do it easily or cheaply, but it is possible. They haven't done it, they haven't developed robust systems, and now they can't instantly resolve the problem.
I mean, let’s assume that this problem is as simple and everything else on the ground and with scheduling works perfectly (which it isn’t and everyone here is rightly calling you out on. Ever work in an operations environment? Shit goes wrong fast).
You still have to contend with the laws of physics. AKA the speed of aircraft and distance between airports. Compound that thousands of planes making potentially cross country trips and it will take days to do what you are suggesting, leading to the same problem SWA is already facing.
So you need to choose destinations for a few thousand planes?
No. You need to figure out which planes are where, which of those planes are legal to fly out of which airports, which planes can be made legal to fly with low effort, and which planes need to go in for service (potentially requiring a non-revenue flight).
Ostensibly Southwest operates a fleet entirely of Boeing 737s with two subfleets (ETOPS and non-ETOPS). The ETOPS planes can be used anywhere but the others cannot be used to Hawaii. Some of the ETOPS routes require the range of the MAX and some do not. Some of the airports Southwest flies into can only handle the smallest planes. It's entirely possible that everything stuck in Oakland is too big to fly into Burbank for instance. Or its entirely possible that all of the ETOPS fleet is stuck in Hawaii (so all of the routes too Hawaii are no-gos).
Then you've got to figure out what's broken on each plane. Depending on what's inoperative a plane may not be able to fly into a specific airport if the weather is anything but perfect. If enough stuff is broken the plane may be stuck away from a maintenance base and illegal to fly in revenue service. There goes a plane and a flight crew. These are laws, not optimizations.
And finally you need to figure out where all the diverted flights went. No idea what's normal but Southwest had to divert two flights today (one due to mechanical issues and one due to an unruly passenger). So there's at least one plane that's out of position and unable to fly until it's been repaired.
Need captains familiar with the airports?
No. In fact I'm pretty sure that unlike RyanAir and EasyJet, Southwest doesn't fly into any airports that categorically require specific familiarity and training beyond the ETOPS certs required for flight and maintenance crew on the Hawaii routes. You do need to figure out who's legal to fly in revenue service and who might be legal to fly on a ferry permit though. Southwest was pretty late to the autopilot game but at other airlines some captains are qualified to land in worse weather than others. So even if you have a flight crew ready to go they may be unable to complete your desired route today – and that's been a problem. The Southwest scheduling software assumes that every pilot completes their assigned flights successfully. Whoops.
Then you've gotta do the same with the cabin crew. And then you've gotta make sure none of this runs afoul of the various CBAs. The baggage handlers? They've been working without a contract for nearly three years and were threatened with immediate termination by Southwest's VP of ops. Wanna guess how strictly the ramp rats will stick to the letter of the contract?
And you haven't even addressed the issue of out of position luggage. It's not just that luggage is piling up at airports, but Southwest's actually flown some of the luggage without the passengers. The hand waving I've seen suggests that Southwest still does a lot of the luggage tracking manually.
When that's all said and done you're still going to need to handle everything that goes tits up as service resumes. As I pointed out earlier, Southwest had at least two diversions today. So now you have two more out of position planes, crews, and more out of position luggage and passengers.
It's a massively complex, dynamic problem. If a couple million bucks would solve things, Southwest would've spent it already. List price on a single 737 is around $40 million. Even if Southwest got half off you're still talking tens of millions of dollars per plane. Put another way, Southwest has so far bought two airlines only to junk their entire fleet. A few million here and there is nothing, especially if it could've headed off this chaos.
People who manage electric grids have protocols for “black starts”. These protocols are
messy and complicated, but they are developed in advance, and they work. Airlines should
have the equivalent capability.
Most airlines do but, based on the anecdotes from Southwest crew, Southwest does not. Again it's not really that Southwest flies point-to-point, and it's not just a software issue at this point. Procedures that worked when Southwest was a scrappy little airline simply don't scale and Southwest management is ill-equipped to handle this. It's all compounded by the employee contempt that Kelly's managed to foment.
But this is HN, and, from an optimization / constraint satisfaction problem perspective / scale perspective, it’s really not a very large problem. The “going home” problem is a standard programming contest problem. This is more constrained, but a globally optimal solution isn’t needed. Southwest literally has a program called SkySolver. It should work.
So you need to choose destinations for a few thousand planes? Pick the place you would normally have them at 4 AM two days hence. Need captains familiar with the airports? Surely the captains who would normally fly from a given airport at 4 AM two days hence are familiar with those airports. This gives a good starting solution for further optimization.
You need to get a message to ~20k people? Great, Twilio will do that with minimal effort.
Will a budget of a couple million dollars, this is not hard. There are good SMT solvers available for free. CPLEX is expensive but not on this scale. Managing test cases on this scale is straightforward.
Even in an emergency, something good enough to get to the point where SkySolver starts working again should be doable.
People who manage electric grids have protocols for “black starts”. These protocols are messy and complicated, but they are developed in advance, and they work. Airlines should have the equivalent capability.