Gospel Prism

Justin Taylor blogged about this, but Farecast.com might be the best airfare deals site there is out there. Here’s what they do:

Fare Prediction and Fare History – Know when to buy

We predict where fares are going and show where they’ve been—now for more than 75 home airports (indicated in green within the search form). Here’s how it works:

Fare Prediction

A Fare Prediction shows if the lowest fare is rising or dropping over the next seven days for the specific dates and cities searched. Each prediction includes the following elements:

1. Arrow: An indication of whether the lowest fare is rising, dropping, or staying the same.
2. Confidence: A percentage based on our track record for similar predictions for the market searched.
3. Average Fare Change: An amount reflecting the average fare change recorded when similar predictions were correct for the market.
4. Buying Tip: Our recommendation based on the prediction information.

Fare Predecition Sample

Fare History

Fare History charts the lowest fare observed each day for your trip, up to 90 days ago. In other words, it’s as if you would have searched for your trip every day and plotted the lowest fare actually available. To provide the airfare history, we have made more than 90 billion, and counting, airfare observations based on real pricing and availability.