the Mandatory Participation rule
 

A core tenet of CRS rules in the EU today is the requirement of airline-owning CRSs to participate equally and fairly in competing CRS systems. Thus, for example, Lufthansa must participate in the Galileo CRS system because it owns a significant stake in the Amadeus system. If this were not the case, travel agents in Germany, for example, would have little choice but to use the Amadeus system.