American Airlines has filed fresh papers in its antitrust suit against Sabre in the US, raising the stakes by claiming the technology company “used its market power to hinder the sales of tickets on American flights”.

In its latest filing, American accuses global distribution system (GDS) Sabre of using “anticompetitive contract terms, discriminatory refusals to deal, punitive bias actions and secret collusive boycott agreements . . . to unlawfully maintain its monopoly control.”

The carrier says: “Sabre not only engaged in unlawful behaviour, but served as the ring leader in a classic hub-and-spoke conspiracy.” The documents suggest that as early as 2006, “Sabre demanded terms that impede American’s ability to develop ‘direct connect’ alternatives to the GDSs”.

American’s lawyers argue that in January this year, not only did Sabre implement “system-wide biasing of its display of American’s fares and flight data” – which led to the original lawsuit – but also: “Sabre was secretly organising a group boycott.”

Sabre is the biggest GDS in the US and largest seller of American flights in the carrier’s home market, accounting for $7.7 billion in sales of American Airlines’ flights in 2010.

A spokesman for American said: “We believe evidence will show that, among other illegal behaviour, Sabre has used its market power to inflict harm on American by hindering the sale of tickets on American flights. The sole purpose was to preserve its monopoly position by deterring American and others from continuing to pursue cheaper, more flexible means of distribution.”

Sabre has filed a counter antitrust claim against American, arguing that: “American is unlawfully forcing travel agencies, travel management companies and corporations to take its Direct Connect product in order to access the airline’s full fare information.

“American Airlines is attempting to eliminate the GDSs . . . by refusing to provide complete fare information to GDSs and by forcing travel agents to use its direct connect product instead of GDSs.”

Sabre Travel Network senior vice president Chris Kroeger said in June: “Sabre has no choice but to pursue legal remedies. Having failed to gain market acceptance of its Direct Connect product, AA chose to go outside the bounds of fair competition.”

The case, filed in a Texas state court, is not expected to reach a conclusion until next year. In the meantime, American and Sabre have extended their existing full-content agreement so that American fares remain available via the Sabre GDS. The deal had been due to expire at the end of August.

American is also engaged in antitrust litigation in the US with Travelport, owner of the Worldspan and Galileo GDSs.