The CT 100 is based on 2015 air tickets purchased for domestic or international business travel at all U.S. points of sale. Most organizations listed 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. In their online questionnaires, respondents were asked to list their organization's highest-volume suppliers and other preferred suppliers in the United States and in other regions; their responses are included by supplier category and alphabetically in the listings as "principal suppliers."