I have used a service from a start-up named Yapta, which mainly offers flight price track system for the customers. Once you decide which flight you want to take in the future and set up the price alert, they will send email and tell you the trend of the ticket price.
I hear about the service from one of my friends who also like traveling.
So I decide to choose this over an alternative product for several reasons: (1) the product is free to use, so you don’t need to pay extra money to get the service you want. (2) Unlike other similar products, Yapta offers both the price change and the price trend, so the customers can plan in advance to see the trend of price change and then find the best price. (3) Yapta also include a refund system, so once there is a price drop for your ticket, the customer can receive the refund if they track the ticket they have bought.