How many hours in advance can I do online check-in?
an-TI-ci-po — stress on second syllable. 'Online' is used as in English.
When planning your pre-travel routine and wanting to know the check-in window.
'Da quante ore prima' (from how many hours before) is a natural Italian way to ask about advance timing. The structure 'da quanto tempo' / 'da quante ore' is used for duration or advance notice questions. Online check-in windows vary by airline from 1 hour to 30 days before departure.
Il check-in online chiude quanto tempo prima del volo?
How long before the flight does online check-in close?
Usually 30-90 minutes before departure
Posso fare il check-in in aeroporto anche se ho già fatto quello online?
Can I check in at the airport even if I already did it online?
Usually only needed if you have bags to drop
Ho già fatto il check-in online, devo solo imbarcare il bagaglio.
I already checked in online, I only need to drop my bag.
Go directly to the bag drop queue
Most Italian and international airlines serving Italy open online check-in 24-48 hours before departure. ITA Airways opens at 48 hours, Ryanair at 24 hours. Printing your boarding pass or saving it to your phone's wallet is strongly recommended before arriving at the airport.