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 most popular airlines on the route Thessaloniki - Barcelona: Ryanair (FR), Aegean (A3), Turkish Airlines (TK).
The cheapest flights you can book on the route Makedonia (SKG) - El Prat (BCN).
There is no direct flight on the route from Thessaloniki to Barcelona
Il volo con scalo più breve dura 7h 40min.