The Corporate Travel 100 is based on 2018 air tickets purchased at all U.S. points of sale for domestic and international business travel. Many organizations provided at least some information for use in their specific listings. Respondent organizations completed an online questionnaire; some provided additional information in interviews. For organizations that did not participate, BTN used industry sources, published reports and other intelligence about specific programs to provide an estimate of U.S.-booked travel spend. Estimates are noted in the listings. In the online questionnaires, BTN asked respondents to list their organizations’ highest-volume suppliers and other preferred suppliers in the U.S. and other regions; their responses are included by supplier category.