The best time to buy flights for Christmas travel depends on a variety of factors. If you are planning to travel within the United States, the earlier you book your flight, the better. However, if you are planning to travel internationally, it is important to keep in mind that the holiday season is one of the busiest travel periods of the year, and the cost of flights will likely increase as the travel dates get closer. Therefore, it is advisable to plan your trip and book your flights at least a few months in advance.