Abstract: The invention relates to a system for the online auctioning of preferential travel fares, formed by: the information servers of different travel providers, the communication computer terminals of the corresponding passenger access control posts, and the mobile communication devices of passengers that paid non-preferential fares, such as smart phones, personal digital assistants or tablets, all interconnected via the Internet to a website hosted on an external HTTP or HTTPS server managed by an auctioning/bidding web application. The system is an effective means of selling the largest possible number of previously unsold business or first class tickets in the moments prior to the departure of an aircraft or transport vehicle, thereby increasing the profitability of each trip and allowing passengers with ordinary tickets to travel in business or first class for a lower fare.