How operating one type of plane makes recovering from disruption harder? I'd expect it to make it easier - you can replace any crew with any other crew, and any plane with any other plane. Same with secondary airports - I am not sure how it makes recovery harder. Distributed systems are usually more robust against disruption that centralized ones - if you can't fly in an out of the hub, then all your flights in that hub's vicinity are grounded, but if you just lost one secondary airport, there might be another close by. So I'm not sure I am convinced those particular qualities are detrimental to robustness, at least without a convincing argument.

well, as an example, when the 737MAX was grounded, many airlines had already started taking delivery of them and were operating them. Southwest was the largest recipient at that time.

Southwest had plenty of older 737s as well, but the new MAX planes both fly farther and have more seats, so while the grounding was in effect Southwest was essentially paying to keep the things on the ground while scrambling to reconfigure their flight network, and it affected them the most.

Single AC fleets mean an airline has somewhat of a single point of failure. If the issue at hand is caused by that point of failure, sure recovery will be harder. In most other cases it makes it actually easier, at least on paper. No need to get crews to certain planes, just a crew to a plane, as every crew is certified on any plane.

And people wonder why Boeing made such an effort to not need different pilot training for the MAX.

People don't really wonder that though. The potential for it to be beneficial to their customers is obvious.

I wondered always why people wondered. Airbus went to great length to make cross-certification of pilots possible for that very reason.

Nobody is wondering anything. Advantages are obvious. They were wondering why you’d prioritize that over the aircraft’s ability to stay in the air.

I've followed many 737MAX threads on HN, and they sure did dismiss this issue. It was always "why didn't they design a whole new airplane from the ground up".

> why you’d prioritize that over the aircraft’s ability to stay in the air.

This is an egregious misunderstanding. There was nothing wrong with the purpose of the the MCAS system nor the concept of it. What went wrong was its failure to follow the dual path design, and do a proper failure analysis of its design. There was a further problem with some pilots not understanding how to deal with stab trim runaway.

These problems have since been corrected, and MCAS is still on the 737MAX.

To be fair, there is more than one way to skin a cat, though it wouldn’t have worked for Southwest.

They could’ve made a small sized aircraft that had commonality with the 787 rather than the 737.

IIRC a few 737MAXs fell out of the sky. Clearly there being nothing wrong with the purpose nor concept of MCAS wasn't sufficient to keep the airplane from crashing.

MCAS in itself doesn't seem to have been the problem. The fact that MCAS relied on a single sensor (no idea how that got certified in the first place) and that pilot were not aware of MCAS and how it worked were the problems. The latter was due to Boeing trying to avoid re-training and re-certification of air crew.

> pilot were not aware of MCAS and how it worked were the problems

If the pilots followed runaway trim procedure, which is how the MCAS failure manifested, they would have been fine. In fact, that's what the other unmentioned crew of a 737MAX did that survived MCAS malfunction and landed without incident.

Boeing issued an Emergency Airworthiness Directive about the procedure, which the Egyptian Air pilots didn't follow, either.

I thought there were some conditions in which manually adjusting trim became physically impossible (or at least extremely difficult).

If the wheels fall off your car, is the problem with the purpose or concept of wheels, or is the problem with weak axles?

Errr... I never said anything at all was wrong with MCAS.

The utilization rate is so high that specific planes and crew are needed in specific times and places.

If plane going from A -> B is late it cannot become flight B -> C. If crew for this plane are stuck in the ground long enough, they have to wait til the next day to fly as they‘re only allowed to be awake and work for so long.

> Distributed systems are usually more robust against disruption that centralized ones

Distributed systems can also be more complex to re-converge after a major disruption.

I'd imagine it's non-trivial to re-plan a network, given equipment and crew limitations.

And as context, we're talking about 24 hours later, now?

Yeah. Part of Southwest‘s high utilization rate is their ability to turn around planes and crew quickly.

In the event of widespread disruption, planes will not make it to their next airport to become a different flight, nor will their crew. Crew can also only be awake and working for a limit of time, so if the disruption causes a crew to go over that limit they are not going out until the next day, etc.

With cloud computing, it‘s a bit different because which host you‘re using in a region doesn‘t really matter, but for airline a specific plane with specific people need to be in a specific time and place.

But not using the same plane would not make it any better, neither would using a hub - that's my point. This is a common problem, but the properties outlined in the parent post which are supposedly specific to SW do not make the problem worse.

Maybe it's the same effect as happens with monoculture (https://en.wikipedia.org/wiki/Monoculture#Risks): more efficient, but more fragile/risky?

They used to be a low-cost carrier but they're pretty average now in terms of cost. They've been replaced at the lower-end by Spirit.

They're no longer low cost because of service erosion at the main carriers (squeezing more seats in, getting rid of baggage allowances, etc.). As a result of that erosion and southwest's holding the line, they are now one of the higher quality carriers (and some would say one of the best!). An interesting course of events to get us here...

Spirit & Frontier (and Ryanair in Europe among others) are actually classed as ULCC's (ultra low cost), where everything is nickel and dimed.

At the higher end, it certainly isn't necessarily the best any more, but I do think that's mostly because Southwest has kept to its two free checked bags, whereas the major carriers now make significant revenues from checked bag fees.

It took one trip for Spirit to go onto my personal No Fly list.

While Southwest remains my favorite airline.

I took my first and last Spirit flight ~7 years ago to fly cross-country. It honestly felt at some points like the plane was going to fall out of the sky.

And Frontier. They're the first one that comes to mind when I think "cheap".