AMSTERDAM, NETHERLANDS - APRIL 23: A United Airlines and several KLM airplanes are parked on the tarmac in Schiphol Airport on April 23, 2017 in Amsterdam, Netherlands. Schiphol is the main international airport of the Netherlands. It is the third busiest airport in Europe in terms of passengers, and the hub for KLM and its regional affiliate KLM Cityhopper as well as for Corendon Dutch Airlines, Martinair, Transavia and TUI fly Netherlands. The airport also serves as a European hub for Delta Air Lines and Jet Airways and as a base for EasyJet and Vueling. (Photo by Horacio Villalobos - Corbis/Corbis via Getty Images)