When an airplane model that has already suffered two fatal crashes, required multiple fixes and been grounded for almost two years then has a hole blow open in midair — sucking out people’s belongings and turning their flying experience into a harrowing microburst of gushing wind — the obvious question for the casual flyer is why on Earth airlines are still asking them to buy tickets to board this jet.

I received multiple questions along these lines after an unused exit door that was meant to be sealed shut on a Boeing 737 Max 9 plane flown by Alaska Airlines instead ended up in a school teacher’s backyard, prompting the United States' Federal Aviation Administration (FAA) to temporarily ground the aircraft variant on Saturday and require immediate inspections of about 171 jets.

It is still unclear exactly why the fuselage panel ripped off soon after takeoff, although early evidence points to a manufacturing glitch or oversight rather than a design problem. The plane involved was brand-new, having been delivered to Alaska Air Group in October. Boeing Co. already had to slow deliveries of the Max last year after discovering that supplier Spirit AeroSystems Holdings Inc. — which makes the body of the jet — had improperly installed certain rear fittings that attach the vertical tail and drilled oblong fastener holes in a component that helps maintain cabin pressure.