Best flight search engines compared — Google Flights, ITA Matrix, Skyscanner, Kayak, Momondo, Kiwi and Skiplagged for cheap fares.
The cheapest fare is rarely on the first site you check. Flight search engines pull from different inventory, so the same route can vary by a couple of hundred dollars depending on where you look. The smart approach is to use two or three tools together: a metasearch engine to scan the market, then book direct with the airline once you've found the route.
Google Flights and Skyscanner are the best all-rounders for browsing. ITA Matrix is the power tool — it exposes fare construction and routing tricks the consumer sites hide, though it doesn't sell tickets. Kayak's filters are the strongest in the business, Kiwi stitches together budget airlines that don't normally cooperate (great for nomads, but verify before booking), and Skiplagged surfaces hidden-city fares for the risk-tolerant.