Aim to book 30 to 90 days before departure. Prices on average bottom out around 38 to 44 days out.

According to extensive studies by platforms like Google Flights and Expedia:

The best time to buy cheap airline tickets is within the statistical "Goldilocks Window"— and 2 to 8 months in advance for international flights .

Plan further ahead, ideally booking 2 to 8 months in advance. For example, European trips usually offer the best pricing around 3 to 5 months prior to departure.