I had some PM requesting clarification of the check-in process at SCL for IPC-bound flights. So here goes...

As the SCL-IPC leg is officially a domestic flight (though it continues on to PPT) you'll need to use the domestic check-in area. LA Comodoros or OW Emeralds can use the Comodoros check-in desk (alternatively, if you're flying business class I suggest asking if you can check-in here too and bypass what can be long domestic queues).

NB Don't attempt to use the premium check-in area at the end of the terminal building as this is for international services only.

At check-in ask if it would be possible to use the lounge. Your BPs should be stamped accordingly so that you can pass through international immigration controls to the Sala VIP. As observed by others on this thread, that doesn't mean you won't face a challenge from immigration officials - many of whom don't seem to understand that LA has this arrangement to let departing IPC pax use its Sala VIP, which is located in the international departures area. All that should be needed is the correct stamp on your BP, however occasionally you'll need to go back to the check-in area and request an escort.

When it's time for boarding, someone will come and collect you from the lounge and walk you to the plane.