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 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.
this is certainly a complicated situation.
it’s really not a very large problem
So you need to choose destinations for a few thousand planes?
Ostensibly Southwest operates a fleet of Boeing 737s with two subfleets (ETOPS and non). 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?
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.
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.
When that's all said and done you're 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.
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.
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.
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.