What are ancillary services in travel?
Ancillary services are the optional products sold alongside a flight or room — checked bags, seat selection, meals, lounge access, priority boarding, Wi-Fi or insurance.
Ancillaries are a major revenue source for airlines, especially low-cost carriers, and increasingly for hotels and other suppliers.
How they are sold
In traditional channels, airline ancillaries are booked as special service requests and paid through an EMD. In NDC channels, they appear as services inside offers and orders. Some are included in a fare family; others are chargeable.
Platform design
Selling ancillaries well needs post-booking flows (add a bag later), clear display of what is already included, and servicing rules for refunds when a flight changes. Treat each ancillary as an order item with its own state rather than a free-text note on the booking.