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Boeing 737 Max planes are grounded after a hole blew in one mid-flight
(www.theverge.com)
This is a most excellent place for technology news and articles.
I mean I'd argue it's only 30 years since NG, but that's a different argument. It's not like it isn't a proven airframe that still goes through continual process improvements. They certainly could have done things differently, but way more time and cost.
I don't think they know the exact cause and they grounded them out of an excess of caution. I'm going to guess a process got bought off that wasn't complete. That's the kind of thing that's engineered to not fall off if it's properly installed.
We'll see how things pan out in the next few days.