This annual publication provides the best single source of information and intelligence on ancillary revenue, a la carte services, and commission-based travel products, for the world's airline industry. Ancillary revenue for 75 airlines is presented as total revenue, a percentage of airline revenue, and on a per passenger basis. The results reflect 2021 disclosed financial activity.  The narrative for each airline features disclosures made in financial filings, investor presentations, historical results for 2018-2021, and information gathered from websites.  The publication has 145 pages.