In designing an aircraft, there are specific load criteria that must be met. Achieving those goals isn't always that easy, however.

Ideally, you could build an airliner that, when flown at 150% of design load, would fail at every single point. It would disintegrate into dust.

That's kind of tough to design.

So, there is always an Achilles Heel or other critical point that ends up being the first to break. Often, it is a wing root, horizontal stab root, engine mount (wing-mounted engines), or rarely, the fuselage (in long-bodied airplanes).

The issue has become clouded since, in two highly-publicized Airbus crashes, the entire vertical fin has been recovered, intact.

The first was a case of pilot-overcontrol. No one knows what caused the second. Maybe smacking the water was 300% of the design limit-load.

I still think both Boeing and Airbus build good airplanes. And I echo the other posts that computer modeling of stress and strains is only as good as the model.

And the A-320 is still my favorite airliner to fly, from a pilot-comfort and logical systems presentation standpoint.