The scope of the deal was included in a monthly Airbus order tally last week but the name of the customer was not disclosed.
Such a deal would be worth $1.3 billion (1.02 billion pounds) at the most recently published 2018 list prices or about half that after typical discounts. Airbus stopped publishing list values this year.
An Airbus spokesman said the planemaker does not comment on any commercial negotiations with airlines.
Sky Airline also declined comment.
Sky Airline was founded in Chile in the early 2000s by Jurgen Paulmann.
After he died in 2014, its leadership was passed to his son, Holger Paulmann, who transformed the carrier into an ultra-low cost player, a type of airline that relies on unbundling fares and selling multiple optional extras on top of bargain prices.
Sky Airline already operates a fleet of 23 leased A320-family aircraft, according to Airbus data.
(Reporting by Marcelo Rochabrun, Additional reporting by Tim Hepher; editing by David Evans and Jane Merriman)