Source: Data from CheapAir.com.
Average Price of a Domestic Airfare Based on Advance Purchase, United States, 2013
Airlines are practicing a yield management strategy where the airfare will vary as the date of departure approaches. At the aggregate level, it appears that 54 days before the flight offers the lowest fares and that fares are the lowest within a 30 to 100 days window. The most expensive time to book an airfare is the day before the flight is scheduled, particularly if the flight is almost fully booked. Airlines are obviously capitalizing under such circumstances on the willingness of last minute travellers to book a specific flight (often for urgent personal or business purposes where price is of lesser consideration). Airfares are constantly changed to reflect the changing dynamics between supply and demand. On average in the United States, the airfare on a specific flight will be changed 92 times between the time seats are first made available and the departure time.