http://www.businessinsider.com/r-airlines-try-to-woo-customers-back-to-their-own-websites-2015-9

Airlines are trying to draw passengers away from low-price comparison sites and back to their own home pages, seeking to boost profits by selling them extra services such as additional legroom or access to airport lounges.

Airlines across Europe and the United States are experimenting with strategies to bring travelers back to their own websites. These range from improving the booking process to adding fees for tickets booked using third-party distributors, which themselves charge airlines for their services.