The U.S. says it would slap tariffs on European goods unless the EU stopped "harming U.S. interests", but the European Commission says the U.S. had lost most of its claims and that much of the aid faulted by the WTO had expired in 2011.
The WTO ruled that Airbus had failed to mitigate the damage to Boeing from illegal subsidies used to develop the Airbus A380 and A350 jets, according to media reports.
"Today's final ruling sends a clear message: Disregard for the rules and illegal subsidies is not tolerated", Boeing CEO Dennis Muilenburg, said in a statement.
The WTO has yet to rule on a related case charging that tax breaks by the U.S. state of Washington - where most Boeing manufacturing facilities are located - amounted to an illegal subsidy, the release said.
The decision by the WTO's appellate body comes as the Trump administration has exerted intense pressure on the Geneva-based organization over what the president alleges is its "unfair" treatment of the U.S.
"This is expected to be the largest-ever WTO authorization of retaliatory tariffs", it said in a statement.
The decision could further ramp up tensions between the US and Europe, which have been stoked by President TrumpDonald John TrumpAvenatti defends right to release Cohen's financial info Pruitt's 24/7 security requested over fears of Trump policy backlash Senate GOP anger over McCain insult grows MORE's criticism of EU trade policies, his refusal to provide a permanent exemption for tariffs on European steel and aluminum imports and last week's decision to leave the Iran nuclear deal.
The ruling centres on actions taken by the European Union generally, as well as four of its member states: Britain, France, Germany and Spain. Boeing claims that the EU provided the European aerospace giant more than $22 billion in illegal subsidies.
A WTO panel and the Appellate Body had already. It also upheld a ruling by the WTO's compliance panel that the launch aid continued to exist after December 1, 2011, the day that the European Union was supposed to comply under a previous decision.
Airbus shares fell shortly after the WTO issued its findings and were poised to close down around 0.86 per cent.
It has been predicted that the tarrifa of Boeing could reach billions of dollars a year starting as early as 2019.