I have mixed emotions about how much to blame the airlines in this case.

I think it's fair to say that a lot of people - internal at Boeing, FAA regulators, national agencies around the world, and airline purchasers - will all be reviewing their processes after the MAX fiasco. However, of that list I hold the airlines the least accountable.

I think the question comes down to one of reasonableness; just how deep into the aircraft design is it reasonable to expect for the airlines to dig, before they purchase a new plane from the manufacturer?

• Should they understand the basic operational characteristics of the plane? Of course.
• Should they follow the manufacturers guidance relating to minimum pilot training requirements? Yes.
• Should they inspect the physical plane upon delivery and ensure there are no manufacturing flaws? Absolutely
• Are they required to re-validate every single engineering decision that was made during design? No, I don't think that's feasible.
• Are they expected to conduct their own code reviews of all software running in the plane? Of course not.

In the case of the MAX, the specific flaw that brought down the planes was primarily a software design issue, buried deep within a system that may not even have been revealed to the airlines (I know there's ambiguity about that point). I can't see any way that the airlines should have been expected to uncover that problem.

If the airlines did know about the existence of the MCAS system, then it's reasonable for them to have asked why that system was there, what it did, and possibly even some of the questions we're asking now (were alternative designs considered, etc) ... but even for them to have asked "how many AOA sensors does this system use to drive activation" is a pretty deep question for them to have asked.

As I said, I think that a lot of people will all be reviewing their processes after this, but I can't think of any similar precedent for this situation (certainly not recently) that would have motivated those sorts of detailed questions, last year (aka, before the first crash).