We do not have enough data on this route to provide a reliable graph showing how many days before departure it is the best to book.
However, usually the closer it is to the departure, the more expensive the tickets are.
The cheapest flights are on the route San Franceso d'Assisi (PEG) - Charleroi (CRL).
Direct flights last about 2h 5min.
Direct flights available on: Saturday.
Direct flights: Ryanair (FR).