Farecast is a service that predicts airline pricing in the future (U.S. domestic market only), helping customers decide if they should purchase a flight now, or wait. They’ve been testing a product which allows users to lock in a price found on the site for up to a week. For $10, customers will be protected against any price increases for that flight. This is, effectively, the purchase of an insurance policy against the risk of future price increases.
They have a detailed description of how it works, and how they mitigate their risk, on the Farecast blog.
We’ve liked Farecast since we first covered them, but note that some of the most competitive airlines, including SouthWest, don’t allow services like Farecast to access their flight data and sell tickets. We recommend using Farecast and other sties to look for exceptional deals, and then compare those prices to SouthWest and other discount airlines to determine the best ticket for them.