On average, from most locations, when planning your trip to Cagliari, try to book your flight in the region of 60 days in advance for the cheapest prices.
In general, booking your departure to Cagliari for a Tuesday represents the best deal on airfare. Try to avoid a Friday departure to stay away from the highest prices.
Typically, cheap prices to Cagliari are most often found for morning flights. Cheap prices are less likely for afternoon flights.