Google Flights data collected between 2021 and 2025 shows that the cheapest days to depart are Tuesday, Monday and Wednesday, with prices up to 20% lower than on weekends. Buying tickets between 21 and 52 days before travel usually yields the biggest savings, but for international flights it is wise to buy your ticket 50 – 101 days before departure. You can save even more by choosing connecting flights and turning on price tracking. When and on which day are airline tickets the cheapest?!