With the exception of the occasional nature orientated aircraft disaster humans are always involved all the way down the line from faulty or fake parts (the latter still being a big problem for the airline industry) through to dodgy mechanical repairs and servicing, refueling errors, terrorism, sabotage, pilot error and pilot suicide. Choose your poison - concocted by humans. Coincidently, for the last couple of months I've been doing some simple vicarious research on plane crashes for a fiction writer tapping my contacts in the airline industry; a book where there is only one survivor due to the plane being sabotaged by a psychopathic husband and aircraft mechanic that has found a new gal and wants to inherit the house - murder being a not uncommon scenario in spousal disharmony. So, yeah, 95% of the time for a myriad of reasons humans are the prime candidate for the cause of airline crashes.
