The Golden Rule of Flight Booking is straightforward: budget travelers should not book flights less than three weeks before their departure date.
When should I buy my airline ticket to get the best price?
You should buy your ticket during the "prime booking window." The prime booking window varies from year to year, but it generally falls between three and four months.
Book on a Tuesday; leave on a Wednesday.
This is still the golden rule of flight booking! Make your actual booking on a Tuesday and, if possible, be flexible enough to fly on a Wednesday. At the very least, enter the booking process with a two-day "window" for your departure and return dates in order to take advantage of airline website calendars that show daily fare changes.
Book six weeks in advance.
This time period has been shown to be the most effective for domestic flights. Booking international flights four to six months in advance is recommended. After you've booked your flight, make sure you get the seats you want. You should not leave this crucial aspect of your travel day to chance!
Book two 1-way fares on different airlines
Many airlines offer extremely low one-way fares. Passengers then discover that the return flights are very expensive. To avoid this problem, book your inbound flight on a different airline than your outbound flight.