1. Expedia
12/12Expedia Group, which owns Hotels.com, Vrbo, Trivago, Orbitz, Travelocity and Hotwire, among a plethora of other brands, reported $107.9 billion in sales last year. More than 40 percent of transactions across the group's consumer OTA brands were booked via mobile, with total app transactions jumping more than 40 percent year over year.