High-stake online travel agency competition used to merely revolve around how many tens of thousands of hotels, or homes and apartments each company added to its ranks during the previous quarter, and those milestones are still very much in play.

But lately, a new and somewhat more esoteric flashpoint has emerged, namely the connected trip. Enter Booking Holdings and Expedia into this fray.

Travel industry executives have referred to the concept by various names, including the connected trip, the perfect trip, even frictionless travel, and the idea has been bandied about for years.