Besides the primary Kayak service, Kayak also operates six other brands. Kayak also maintains travel-related data used to track the state of the airline and other travel-related industries. Kayak is owned by Booking Holdings (formerly Priceline).
Kayak is an online travel agency and search engine founded in 2004 by Steve Hafner and Paul M. English as a Travel Search Company and acquired by Booking Holdings in 2013 for $2.1 billion. The company makes money via an advertising model based on cost per click, cost per acquisition, and advertising placements.
You might be cautious of go-betweens or third-party booking sites, but Expedia is a legitimate, well-known online travel agency that's been around for years. Microsoft originally launched the Expedia website in 1996.
Those who buy on Sunday instead of Friday (the most expensive day to shop for plane tickets) will save on average 17% on domestic flights and 24% on international ones.