This. This. THIS! The filters are absolutely fantastic. Not just saying how many people, how many bags you need to add to the costs for each individual airline (in my case frontier may not be your best deal, not just because of the bag, but also if the plane arrives in the middle of the day it's pretty much worthless to me), but using a little slider bar with times you want flights to arrive (great for planning amusement parks without blowing another night of hotels), number of stops, the 'price graph' where you can put in how many days you need your trip to be but find the best days for the price, the most your willing to pay and then you can track the prices of all potential flights in a filter OR an exact flight itinerary if all the things match in your favor, along with alerts in addition to all that. It will tell you if you are paying average, below average, etc. The only thing you have to do is check Southwest separate as they are not part of the aggregate sites. If you need (2 free) checked bags they will be a good deal. There is a slight learning curve but once you know what you're doing it's awesome.