I use an online matrix site that a group of MIT computer scientists came up with in the 90's. It's free and it is always spot on with the prices. You can't book directly on the site, you just call or go online with the airline or your travel agent with the information and book your flights. You can use a numer of search functions and search over a number of days at a time. I use it everytime I travel now. If Rob will allow me to post the link I will....like I said it's free to use.