The World Trade Organization ruled that European loans for Airbus were illegal subsidies under world trade rules, US lawmakers said, but European sources said Washington did not win a sweeping victory.

The decision came in a confidential 1,000-plus page ruling handed out to the US and the European Union at WTO headquarters in Geneva.

The findings will not be made public for months.

Lawmakers from Washington State, where much of Boeing's production work is done, said the WTO agreed with the United States that European "launch aid loans" to help Airbus develop aircraft violated global trade rules.

"I applaud the WTO's decision that government subsidies of Airbus are illegal," said Senator Maria Cantwell. "When finalized, this long-awaited ruling will help restore true competition in the commercial aviation market.

Representative Norman Dicks also welcomed the ruling, which he said "definitively confirms" the US argument in the case.

"But what is discouraging is the damage that has been done to America's premier airline manufacturer, which has suffered the loss of 20 percent of the market share, representing hundreds of billions of dollars in value and tens of thousands of jobs, since our concerns were first raised with the Europeans," Dicks said.

Dicks and Cantwell were briefed on the ruling by US trade officials, their spokespeople said.

European sources said the ruling was not as clear-cut as the lawmakers and US private sector sources claimed.

"The assertion that the WTO report says that all 380 funding is a prohibited subsidy is wrong. The findings are much more nuanced than that," a European source close to the case said.

The Airbus case, and the European Union counterclaim about US support to Boeing, the United States' biggest single exporter, represent the most complex and commercially significant dispute in WTO history.

Washington says Airbus received a $205 billion boost from advantageous loans and other perks from France, Germany, Spain and Britain over two decades, giving it an unfair edge.

Brussels, in turn, argues the Airbus loans were fair and says Boeing got big illegal subsidies from US agencies including NASA plus state tax breaks worth some $24 billion.