Here is how yield management works. For each flight or route (if we are talking about multi-segment itineraries), the airline has a set of available price levels, from the most expensive fully refundable fare to the cheapest deeply discounted, non-refundable price. The industry jargon for these prices is “buckets.” Then, seats can be interpreted as balls that are allocated among these buckets.

Initial allocation of seats between the price buckets is determined by historical data indicating how well a certain flight sells. For example, fewer deeply discounted seats will be offered on a flight on Thanksgiving week than on the same flight during the third week of February. As the seats on a flight sell, yield managers monitor and adjust the seat allocation. If, for instance, the sales are slower than expected, some of the seats might be moved to lower-priced buckets—this shows up as a price drop. As noted above, such price drops can occur at any time before the flight. However, the general trend of price quotes is upward starting from about two to three weeks before the flight departure date.

Of course, an average traveler wants to know when he or she should buy the tickets for the next trip. Another important question is where to buy this ticket. Airlines distribute their inventory on their own websites and on several computer distribution systems, meaning that prices can sometimes differ depending on where one looks. We are not entirely sure what precipitates this phenomenon—likely explanations include differences in contracts between the airlines and the distribution systems or travel agents, implying that different travel agents may not have access to the airline’s entire inventory of available prices.

The airlines’ yield managers start looking at flight bookings about two months before the departure date. This implies that it generally does not pay to book more than two months in advance: Studies show that initially the airlines leave the cheapest price buckets empty, and yield managers may move some seats into those buckets if a couple of months before the departure date the flight is emptier than expected. Between two months and about two to three weeks before the flight date, the fare quotes remain mostly flat, with a slight upward trend. However, and perhaps paradoxically, there is a good chance of a price drop during this period. We tend to monitor prices for several days—sometimes up to a week—hoping for a potentially lower quote. It does not always pay off, but sometimes we do manage to save a considerable amount of money.

Two to three weeks before the flight date, the price quotes start increasing. This is the time when business travelers start booking. While price drops are still possible, a chance of a price increase is much higher if you wait to book within this time period. This is also the time when one can find significant differences between price quotes, depending on where one looks and what contract they have with the airlines.