An appellate panel of the World Trade Organization has ruled that U.S. aircraft manufacturer Boeing received billions of dollars in illegal government subsidies in its competition with the world's biggest planemaker, Europe's Airbus.

Monday's ruling by the WTO appeals panel largely confirmed an earlier finding that Boeing, the second biggest aircraft maker, received support from U.S. federal and state governments that violated global trade rules.

But U.S. Trade Representative Ron Kirk claimed victory in the long-running trade dispute between the two aircraft giants. He said the new ruling supported the U.S. contention that European assistance for Airbus was far greater — with the Boeing subsidy totaling between $3 billion and $4 billion. An earlier decision pegged the Airbus assistance at about $18 billion.

European Union Trade Commissioner Karel De Gucht said the ruling vindicated Airbus as well, proving that Boeing had “received massive U.S. government handouts.”

The dispute is unlikely to end soon, with the U.S. and European governments, as well as Boeing and Airbus, now left to figure out how what kind of assistance can be provided to the aircraft manufacturers.