On LATAM Airlines, you can check-in online, from either the website of the airline or its mobile application.
Online check-in opens 48 hours and continues till 2 hours before departure of flight. This is the cut-off time limit for web checkin or mobile check-in for the airline
Who is not eligible to check-in online?
Passengers with special needs, travelling with infants, groups, not having electronic tickets, requiring documentary check at airport are still required to check-in at airport counter.
Another important case where a passenger might not be able to check in online is when the boarding pass is to be given at the destination airport. These destinations are USA (for LATAM Brazil flights), Australia, Oceania, Bolivia, Cuba and Africa.
When the operating carrier is another airline, even then you are not allowed to check-in online.