Southwest Airlines Looking for Fuselage Cracks in 737s

The Southwest Airlines Way

Apr 4, 2011 — Southwest Airlines on Saturday grounded dozens of its Boeing 737s, after one of them developed a large hole in its fuselagewhile in flight last Friday. The company, along with Boeing is inspecting these aircraft for "subsurface fatigue in the skin that is not visible to the eye."
The NTSB is also probing the cause of the hole and says it found additional cracks in the "lap joint along the fuselage" of the affected aircraft.
The NTSB says that Boeing has indicated that it will be drafting a Service Bulletin to address the problem, and once this is complete the FAA will make a determination whether to make it mandatory for all similar 737 airplanes.

Source: Planet Data