American Airlines has vowed to fight a new back-up agreement between Sabre and Amadeus.
The two companies this week announced an agreement that would enable agents to complete bookings on an airline in the "unlikely event" the carrier withdraws its participation in one of the GDS.
Sabre and Amadeus said the agreement would "ensure continued broad and seamless travel agency access to airline inventory and avoid disruptions that might otherwise develop".
But American Airlines said the GDS did not have the right to redistribute its fares and it would not permit booking through unauthorized sources.
The carrier accused the two GDS of misleading retailers into believing they had solved any potential problems relating to content access.
A number of carriers have suggested that in future they may not fully participate in all of the traditional global distribution systems.