Originally Posted by
tomdodo
I think it also depends on a particular country's regulations. Every time I flew into SCL on BA, seatbelt sign went on 40 minutes before landing, and crew explained it was to do with local Chilean regulations (and possibly crossing the Andes)
I was told on an Aerolíneas Argentinas flight that it's due to the fact that over the Andes in the event of a rapid decompression you cannot descend to a safe altitude where the air is breathable (obviously there's a big old mountain range in the way).
However, turbelence can also be a big issue over mountains due to unpredictable updrafts, so that probably has a big role to play.