Flights found using KAYAK's search can be booked in 1 of 4 ways:  (1) directly with the airline, (2) via Orbitz, (3) via Expedia, and (4) via Cheaptickets.  If you choose to book your flight directly with a U.S.-based airline, you will be protected by that carrier's "guaranteed airfare policy" and can become eligible for a refund if the price drops after purchase.  (Foreign carriers do not have "guaranteed airfare policies" and will not refund you the difference in price if a lower airfare becomes available.) If you choose to book a flight through Orbitz, Expedia, Cheaptickets (or any other third party), you will need to work with that third party to get a refund if your flight becomes available for less.  You can contact the airline directly, but chances are, they will refer you back to where you purchased the ticket.  While Yapta will track the price of flights booked through a third party, it will not alert you to a refund because obtaining one on a ticket purchased through a third-party is not assured and may prove difficult.  In this instance, Yapta will alert you only when the price drops.