American Airlines called Sabre's actions against the airline "punitive" and alleged they are at odds with Sabre's contractual obligations.
Rest assured that American's lawyers won't be getting much sleep this evening.
The airline stated:

Sabre’s actions are discriminatory and patently inconsistent with both its contractual obligations and its professed goal of ensuring full transparency for the benefit of consumers and travel agents. In contrast, the actions only serve to protect Sabre’s market position and attempt to force airlines and travel agencies to rely exclusively on its legacy systems that only lead to higher fares and fewer choices for consumers.
However, an American Airlines spokesman declined to elaborate on how Sabre's actions are "inconsistent" with Sabre's contractual obligations.
American's statement this afternoon came in reaction to Sabre's announcement this morning that it notified the airline that Sabre intends to terminate their contract a month ahead of time, in early August 2011, immediately beging charging the airline increased booking fees and bias American Airlines' flights in the Sabre GDS.
The airline said it continues to work in "good faith" with Sabre, although it characterized Sabre's display-bias actions as "anti-consumer, anti-competitive and harmful to its subscribing agents."
The airline's fares and schedules in recent weeks have been biased in the Travelport and Sabre GDSs, and do not appear at all on Orbitz Worldwide and Expedia Inc. leisure travel websites.
American Airlines noted that its fares and schedules are "widely available" through AA.com, its call centers, "thousands of travel agencies in locations worldwide, online travel agencies such as Priceline.com and metasearch engines such as Kayak.com."
No mention of Travelocity, owned by Sabre, which continues to offer American's fares and schedules.
Meanwhile, an American Airlines spokesman indicated that Sabre's actions against the airline today do not impact Sabre's hosting of the airline's internal reservations system.