Certos grandes agentes de viagens negociam tarifas do consolidador com as companhias aéreas.
O link tem alguns anos, mas não acho que haja algo significativamente desatualizado:
A consolidator will have a contract to sell private fares at a lower price than the published fare. If there's a printed ticket, only "bulk" generally appears on the receipt. They generally can't - or won't - sell the ticket straight to you, but will offer it through a travel agent (including an online travel agent such as Travelocity or Expedia), or agencies such as the ones that advertise in Sunday newspaper travel sections. The agent adds their markup - keeping the margin slim so they're not out-priced by published fares - and passes the remaining savings on to you. True consolidators don't buy in quantity or ahead of time. Rather, they pull availability from their assigned class until the airline decides to close the window.
O artigo da Wikipédia sobre o mesmo:
An airline consolidator is a wholesaler of airline tickets. Airlines use consolidators as a means to reach out to more niche target audiences, and by offering discounts and fare flexibility that is relevant to the target group. Consolidators work through contracts with major carriers to sell at reduced prices