Cheap Air Costs & Explanation

I just found this great photo on Flickr, you absolutely have to read it. It compares the more expensive air costs with the cheaper air costs and shows exactly what you give up or gain when you get cheaper tickets. More importantly for me, it showed me where to go to get the cheapest airline tickets. Here is the image.

The cheapest flights for Americans can be found on Southwest. For English Flights, check out the image and google the name. Do you have suggestions for places to find cheap flights? Or tips for saving on flights?