The NTSB investigation determined that the quality of inspection and maintenance programs was deficient. Fuselage examinations were scheduled during the night, which made carrying out an adequate inspection of the aircraft's outer skin more difficult. The fuselage failure initiated in the lap joint along S-10L; the failure mechanism was a result of
multiple-site fatigue cracking of the skin adjacent to rivet holes along the lap joint upper rivet row and tear strap disbond, which negated the fail-safe characteristics of the fuselage. The fatigue cracking initiated from the knife edge associated with the countersunk lap joint rivet holes; the knife edge concentrated stresses that were transferred through the rivets because of lap joint disbonding. The NTSB concluded in its final report that the probable cause of this accident was the failure of the Aloha Airlines maintenance program to detect the presence of significant disbonding and fatigue damage which ultimately led to failure of the lap joint at S-10L and the separation of the fuselage upper lobe. Contributing to the accident were the failure of Aloha Airlines management to supervise properly its maintenance force; the failure of the
FAA to require Airworthiness Directive 87-21-08 inspection of all the lap joints proposed by Boeing Alert Service Bulletin SB 737-53A1039; and the lack of a complete terminating action (neither generated by Boeing nor required by the FAA) after the discovery of early production difficulties in the B-737 cold-bond lap joint, which resulted in low bond durability, corrosion, and premature fatigue cracking. One of five board members dissented, arguing that "undetected fatigue cracking" was clearly the probable cause, but that Aloha Airlines maintenance should not be singled out within it because the accident could not be "reasonably foreseen" and a "system failure" by the FAA, Boeing, and Aloha each were merely contributing factors. == In popular culture ==