To get the cheap domestic flights, passengers should book their air tickets in advance. How advance is a thing of debate. However, it has been concluded that the best time to book a flight for the winter is 62 days in advance while spring flights need to be booked 90 days in advance. Summer flights can be available at lesser price if they are booked between 47 and 69 days in advance. Airfares of the flights are subject to availability and depend largely upon the flight status on preferred your route and various other factors. These dates don’t guarantee cheap flight fares.