The World Trade Organisation is set to open to the public its hearings in the EU-US battle over billions of dollars in aid for aircraft giants Boeing and Airbus, officials said Wednesday.

The first round of dispute settlement hearings is scheduled for June, and both sides in the tussle have agreed to let the public attend, trade officials added.

The WTO monitors respect for the rules of global commerce, which are set by the 149 trading nations that make up its membership, It also tries to settle disputes among them and can hand out stiff penalties.

Its dispute settlement hearings were previously held behind closed doors, but last year the US, EU and Canada agreed to let the public attend sessions on a case concerning Europe's ban on imports of hormone-treated beef.

The rivals billed it as a way to improve transparency and raise confidence in the WTO, which is often criticised for behind-the-scenes horsetrading.

That WTO first last year didn't provide for a typical public gallery: the audience was able to watch the hearings on closed-circuit television from a separate room.

A similar format is expected this time.

However, there may be "case by case" exceptions which could lead to the cameras being switched off temporarily when confidential business information is under review, officials said.

The US has challenged aid for Airbus from the governments of four European countries -- Britain, France, Germany and Spain.

The EU's complaint hinges on US state and local subsidies or indirect assistance for Boeing.

Washington and Brussels took their cases to the WTO after failing to find common ground in direct negotiations.

But they have also tried to keep open the option of settling the dispute directly, amid warnings that a bitter, drawn out legal clash at the WTO could be disastrous.

The aircraft spat is seen as one of the most complicated that the Geneva-based trade body has ever been asked to handle and could last for years.