[dkarl]

The analogy to code would be if a library had a documented API to do something, but some people were using undocumented behavior in another part of the API to do the same thing, and the undocumented behavior changed. The difference is the consequences and how you prepare for them. With a library, there are many steps at which the change could be noticed by users: issue trackers, mailing list discussions, prerelease builds, integration tests, and test environments. Plus for most software nobody will be killed if the application goes down.

I see Boeing's point, too, but to me it just means both sides are at fault. The pilots are at fault for not following the emergency checklist. Boeing is at fault for abusing rules to slip in a change based on the assumption that pilots never rely on their own understanding of the aircraft, which I'm sure they know to be false. Air safety is all about human factors, and that's a pretty obvious one.