The World Trade Organisation (WTO) is set to make its latest ruling in a multi-billion dollar battle between planemaking giants Boeing and Airbus.
It will give its initial decision over claims illegal subsidies were made by the US government to Boeing.
The case was brought by the European Union which says Washington’s support is anti-competitive.
Earlier this year, the WTO ruled that the EU paid illegal subsidies to Airbus parent firm EADS.
Brussels has appealed against that decision – saying that it would challenge the finding that support for the A380 plane was an export subsidy and therefore illegal.
It added that it would also contest the ruling that there had been a causal link between support to Airbus and adverse effects to Boeing.
The acrimonious tit-for-tat spat has dragged on for almost six years. Brussels brought its case to the WTO in October 2004 – on the same day that Washington complained about EU subsidies to Airbus.
The latest ruling will not be made public as it is only a preliminary finding.
However, an Airbus spokeswoman said that it expected the WTO to “confirm” that Boeing received billions of dollars in illegal subsidies.
She added that this could lead to the two rivals negotiating a settlement.
Some analysts have said that such an agreement would be in the best interests of both companies – allowing them to focus instead on developing their aircraft.
The EU complaint accuses Washington of funnelling subsidies to civil aviation through military research funds.
It claims that the US violated international trade rules by making about $23bn (now worth £14.8bn) of subsidies to Boeing as defence funding.
But Boeing, the maker of the long-delayed 787 Dreamliner, has insisted that all US support was above board.
In a statement ahead of the WTO’s preliminary decision, it said it looked forward to the ruling saying it had “full confidence in WTO processes and its dispute-resolution procedures”.
It added that none of Washington’s actions had “the market-distorting impact of launch aid nor even approach the sheer scale of European subsidy practices”.
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