Boeing 737 cracks are growing faster than expected, forcing earlier inspections

US aviation regulators are proposing tighter inspection rules for certain Boeing 737 airplanes. This means airlines will have to check for cracks in the fuselage skin more often and sooner than before.

Airlines and aircraft manufacturers rely on test data to set maintenance schedules. When real-world data shows a problem is worse than the tests predicted, it forces a change. This proposal means that the original engineering assumptions about crack growth were wrong, and the planes need more frequent checks to stay safe.