NTSB finds more evidence of manufacturing flaw on Southwest B737

US National Transportation Safety Board (NTSB) stated microscope examination revealed fatigue cracks emanating from at least 42 of the 58 rivet holes connected by the fracture in the lap joint of a piece of the B737 fuselage from Southwest Flight 812 (AINOnline, 02-May-2011). Misshapen and misaligned rivet holes in parts of the fuselage removed from the aircraft has lent more credence to theories that a manufacturing flaw led to the eventual failure of the lap joint during an 01-Apr-2011 accident in which a five foot long tear opened in the roof of the aircraft.