Ancillary revenue now accounts for 15.7% of total airline revenue, up from 9.1% in 2016 — but McKinsey estimates $45 billion remains unclaimed industry-wide through 2030. This strategy guide maps the six domains of IATA's Airline Retailing Maturity Index (Shop, Order, Pay, Settle, Account, Setup) against real carrier results in offer and product, distribution, and loyalty. It's built for airline commercial, digital, and ancillary product leaders deciding where to focus their next retailing investment — with three questions to bring to your own team.