For both international and domestic travel, not only are travel agents, consolidators, bucket shops or online retailers important parts of finding the cheapest airfare, but the timing of the airplane ticket purchase is equally important as well.
For U.S. domestic travel, 21 days advance purchase is optimal for scoring the cheapest airfare, although airfares from one major hub to another, e.g., Los Angeles to New York, will not differ greatly between a seven-day advance purchase and a 21-day advance purchase. For international travel, it is best to purchase tickets a minimum of one month in advance, although the earlier the search begins, the cheaper the airfare possibilities. Ninety-day advance purchase for international travel is optimal, if possible.
Airfare is more expensive on Fridays and weekends, so a departure from the point of origin/arrival to your destination during the week--ideally a Tuesday or Wednesday--will result in a cheaper fare.
Holidays are the busiest times for airlines and high demand increases airfare. Holiday travel should be booked far in advance and with date flexibility.
For international travel, booking airline tickets seasons in advance will result in cheaper fares. For example, booking summer tickets to Italy will be cheaper if done by the winter, rather than the end of spring when the demand for tickets increases as does the airfare.
Although this has changed slightly in advantageously affecting airfare cost, incorporating a Saturday night stay has long been noted to decrease airfare.
The time of day or night of purchase has no relevance, meaning the cheapest airfares follow no hourly time pattern. However, airfares can fluctuate by date, so if a cheap airfare is spotted, it should be purchased within 24 hours to avoid a possible price increase.