According to this ABC News report, one of the black boxes (report does not indicate CVR or FDR) from Eastern Airlines Flight 980 has been found and delivered to the NTSB after a prolonged negotiation with the Bolivian government. The 727 crashed into Mount Illimani in Bolivia at an altitude of 19,600 feet on January 1st, 1985. No cause was ever determined.
https://gma.yahoo.com/video/ntsb-exa...211252263.html