Note that rules for changing tickets are often different for the third party websites than for tickets purchased directly with the airline - and the third party websites don't always honor their own change rules (which I learned the hard way, though a little complaint to the DOT helped straighten things out). In short, if anything goes wrong, you will wish you had purchased with the airline. I also use Matrix ITA, then purchase with the airlines (which sometimes takes a little work to come up with the same itinerary).