The subsequent investigation by the [[NTSB|National Transportation Safety Board]] determined that inadequate maintenance led to excessive wear and catastrophic failure of a critical [[Flight controls|flight control system]] during flight. The probable cause was stated to be "a loss of airplane [[Pitch (flight)|pitch]] control resulting from the in-flight failure of the [[Tailplane|horizontal stabilizer]] [[Trim tab|trim]] system [[jackscrew]] assembly’s [[Acme thread form|acme]] [[Screw thread|nut]] threads. The thread failure was caused by excessive wear resulting from [[Alaska Airlines|Alaska Airlines’]] insufficient lubrication of the jackscrew assembly."<ref name="NTSB summary"/> | The subsequent investigation by the [[NTSB|National Transportation Safety Board]] determined that inadequate maintenance led to excessive wear and catastrophic failure of a critical [[Flight controls|flight control system]] during flight. The probable cause was stated to be "a loss of airplane [[Pitch (flight)|pitch]] control resulting from the in-flight failure of the [[Tailplane|horizontal stabilizer]] [[Trim tab|trim]] system [[jackscrew]] assembly’s [[Acme thread form|acme]] [[Screw thread|nut]] threads. The thread failure was caused by excessive wear resulting from [[Alaska Airlines|Alaska Airlines’]] insufficient lubrication of the jackscrew assembly."<ref name="NTSB summary"/> |