In August 1947 a British South American Airways airliner en route from Buenos Aires to Santiago crashed into Mount Tupungato in the Argentine Andes. The wreckage wasn’t located for 50 years, but it’s believed today that, hindered by the jet stream, the pilots had started their descent before they’d cleared the mountaintops and crashed into Tupungato.
The last Morse code message received by the Santiago airport was “ETA SANTIAGO 17.45 HRS STENDEC.” The operator didn’t recognize the last word and asked that it be sent again. The flight transmitted STENDEC twice more and then was lost. The meaning of that last transmission is unknown — despite much speculation, it’s never been definitively explained.