The revamped feature uses data, airline partnerships, and pricing logic to build complex itineraries travelers once had to piece together manually. Consider this: You want to book a multicity, international trip with flights from New York City to London, then Paris, and then back to New York City. There are numerous variables in the mix—different airlines, various ticketing levels, and more—that make the booking more complicated than anticipated. Accordingly, you may end up booking several separate flights, with multiple tickets and confirmation codes to keep track of.