The World Trade Organisation has broadly upheld a ruling that Boeing benefited from billions of dollars of unfair subsidies, part of the world's largest trade dispute that has already revealed significant European aid to Airbus, people familiar with the matter said.

A WTO panel ruled last year that Boeing had received at least $5.3 billion in subsidies through research contracts mainly from the NASA as well as a series of tax breaks.

The findings followed a six-year probe into European Union claims that Boeing had received over four times that amount.

The EU filed the complaint as a counter-suit in response to U.S. claims that Airbus had benefited from decades of European government loans, which the WTO trade body also deemed unfair.

The United States appealed the Boeing ruling while the EU also appealed to try to strengthen certain parts of it.

People on both sides of the dispute, who asked not to be identified, told Reuters the Geneva trade court's appellate body had upheld the bulk of the panel's findings on the Boeing aid.

An advance copy of the ruling has been delivered to both sides and the report is expected to be published on Monday.

It won't change much, but there may be some changes around the edges of the decision, a U.S. source told Reuters. A European source called the ruling a victory for the EU.

The Geneva-based WTO declined to comment.

(Reporting by Tim Hepher. Editing by Jane Merriman)