GENEVA, Oct 23 (Reuters) - The dispute between the United States and European Union over subsidies for the European Airbus is so complicated that the World Trade Organisation (WTO) will not be able to rule on it until next year, a WTO document shows.

The decision prolongs one of the most intractable transatlantic trade disputes, involving tens of billions of dollars, in which both the EU and United States claim the other is giving unfair support to its civil aircraft industry.

Airbus is a unit of EADS (EAD.PA: Quote, Profile, Research, Stock Buzz).

WTO dispute panels usually aim to give a ruling within six months, but the panel on Airbus subsidies was formed in 2005.

"It will not be possible for the Panel to complete its work within six months of the date of composition due to, inter alia, the substantive and procedural complexities of the volume of materials involved in this dispute," said a communication from the dispute panel chairman on the WTO website, circulated to members on Oct. 20.

"The Panel expects to complete its work in 2009," it said.

In July the chairman of the dispute panel formed in 2006 to examine the EU's counter-claim against U.S. support for Boeing Co. (BA.N: Quote, Profile, Research, Stock Buzz) also said his panel would not report until 2009.

There had been speculation the Airbus panel would issue a confidential preliminary ruling this summer, after it circulated a summary of the facts in the case to the parties in March.

Both sides could be found to have violated international trade rules, and Airbus has repeatedly called for negotiations to reach a long-term settlement.

So EADS still can't be sure if their current (and planned?) financing schemes for the A350 will be WTO compliant?

That raises the question of "okay, well what if it is"?

Would they be forced to pay the money back? If so, what time frame? Would that then force them to adjust their prices to an uncompetitive level? Lot of things.