Britain, France, Germany and Spain insisted on Monday that they would continue to offer subsidies to the European planemaker Airbus despite renewed US opposition.
At a press conference held at the Farnborough airshow and attended by European ministers, the quartet delivered a statement that said "the WTO (World Trade Organization) appeal process had confirmed that the mechanisms of Repayable Launch (subsidies programme) investment offered by European nations were not incompatible with WTO rules."
It added: "Ministers are looking for assurances that the United States will comply with the WTO appeal."
The quartet also hailed Airbus' recent announcement to build its first ever manufacturing plant in the United States, home of arch rival Boeing -- a company that benefits from substantial US government subsidies of it own.
Airbus and Boeing earlier this month traded stinging barbs over the controversial state support for aircraft development, accusing each other of bending the rules.
Airbus was first out of the blocks, rejecting claims by its arch-rival that it had caused job losses in the United States, arguing that Boeing itself was responsible for destroying employment.
Boeing responded in kind, charging Airbus with getting six times the government subsidies it had received.
Boeing and Airbus, which dominate the global aircraft business, have been at odds for years over subsidies they receive from their government backers, and both have won and lost complaints filed against the other at the WTO.
Airbus meanwhile on Monday said it planned to build a $600 million (487 million euros) assembly plant in the US port city of Mobile, Alabama, on the Gulf of Mexico, to produce the popular single-aisle A320 passenger planes.
The firm, based in Toulouse in southwestern France, said it would roll out its first US-built plane by 2016.