They difference between the airlines' website and something like Google is that the airline websites will enforce revenue management "rules" that Google won't. As an example, you need to go from AAA to CCC, with a connection required in BBB. The airline sees this as a "journey," not as two separate flights. They sell you the journey, from AAA to CCC, even though (AAA to BBB) + (BBB to CCC) may be cheaper. The airlines are also capable of pricing (or just showing you select seat inventory) based on your previous purchases, maximizing their revenue (minimizing the thickness of your wallet). So, while the airline sites can be good, they are not always good. I always looks at both.