[hef19898]

Cracks are not necessarily something critical. As long as they are identified early enough the affected parts are simply added to the relevant checks (C, D, whatever) and after a predefined number of cycles or hours. Also ad-hoc checks might be required.

Aviation is the standard exactly because defects are identified and handled the way they are, they also tend to be remedied quickly. If not all affected aircraft are grounded, like the 737MAX.

These 737NG cracks can by no means be compared to the 737MAX clusterfuck. The former is pretty normal while the latter is a safety and certification issue of enormous dimensions.