LAN has firmed up a memorandum of understanding for 50 Airbus A320 family aircraft unveiled at the Farnborough Air Show in July.
The aircraft will be equipped with Airbus sharklets, and deliveries are scheduled to begin in 2013.
The order also includes 10 A321s, a type not previously operated by LAN.
LAN has selected CFM56 engines to power the aircraft. The carrier's current of A319s and A320s are powered by IAE V2500 engines.
Flightglobal's ACAS database shows that currently LAN 39 A320 family aircraft on firm order.