The stealth jet is part of the Future Combat Air System (FCAS), which will also include drones, missiles and so-called "remote carriers" that can be used to deliver munitions, scramble communication networks or divert the attention of enemy defences.

French President Emmanuel Macron attended the unwrapping of a full-scale model of the sleek delta-wing aircraft at the opening of the Paris Air Show in Le Bourget, just north of the French capital.

The official cooperation accord launching the project was then signed by the French, German and Spanish defence ministers: Florence Parly, Ursula Von der Leyen and Margarita Robles.

"This project now has a resolutely European dimension: Spain has officially joined the programme this morning," Parly said.

Spain announced its participation earlier this year, but so far no other EU nations have signed on, though officials in Macron's office say talks are underway to bring other nations on board.

Airbus and France's Dassault Aviation are leading the plane's development, aiming to have it operational by 2040, when it will replace the current generation of Rafale and Eurofighter jets.

France's Safran is also developing a new motor for the plane that may include hybrid electric technologies, making the plane quieter while also lowering its heat signature, making it harder to detect.

But Paris and Berlin have still to award an expected 150-million euro ($169-million) contract to begin work on a test plane that could start flying in 2026.

Parly told journalists the contract is expected to be finalised by the end of this year.

The new plane is a crucial test for Europe's ability to forge a joint operational command that could ensure its military sovereignty at a time of growing tensions with the US under President Donald Trump, who has put the solidity of the NATO alliance into question.

Officials will have to win over several EU countries which are longstanding clients of American jets, and which may be tempted by Lockheed Martin's new F-35 stealth fighter.

And the new European jet already has a rival on home turf -- Britain's Tempest stealth fighter project, which has already garnered the support of Italy and the Netherlands.

bur-js/sjw/dl

BOEING

DASSAULT AVIATION

AIRBUS GROUP

THALES

LOCKHEED MARTIN