Airbus is to take over part of the Spirit Aerosystems operation in Belfast.

Spirit is Northern Ireland’s most significant manufacturing employer with about 3,500 staff.

Airbus is taking control of the part of the business which makes wings and fuselage for its A220 jet.

There is uncertainty for the non-Airbus parts of the Belfast business with Spirit saying it will sell them separately.

That part of the business includes a range of work on Bombardier business jets.

The structure of the deal will likely cause alarm among trade unions and the Northern Ireland manufacturing sector.

Earlier this year Sir Michael Ryan, the chair of Spirit in the UK, wrote to local stakeholders warning that “any dismantling of the business would be extremely detrimental to the long-term future of the Belfast business, and by extension, the region’s aerospace industry”.

In the letter, obtained by the Financial Times, he said that while the separation of physical buildings was possible, the company’s structure and ecosystem was “integrally linked” and gave it “economies of scale, providing technological synergies, skills and flexibility”.

Spirit’s wider global business is being carved up between Boeing and Airbus, the world’s largest aircraft manufacturers.

Spirt was founded in 2005 when part of Boeing’s business was spun off as a separate company.

Monday’s deal was initiated by Boeing which wants to bring Spirit back in house as part of its efforts to tackle manufacturing problems.

Boeing is paying $4.3bn (£3.3bn) for its part of the deal whereas Spirit will pay Airbus $559m (£440.6m) reflecting the fact that the parts of the business Airbus is taking over are currently loss making.

Aside from the Belfast operations, Airbus will take control of two Spirit factories in the US, one in France and one in Morocco.

The Spirit operation at Prestwick in Scotland is not part of the deal and will also be sold separately.

Airbus said the deal “aims to ensure stability of supply” for its commercial aircraft programmes, both operationally and financially.

Spirit has been in Northern Ireland since 2019 when it bought Bombardier’s operations.

At the time, that deal ended a long period of uncertainty for the workforce.

Earlier this year Spirit said it would invest in the Belfast factory and hire more staff as it ramps up production for the A220.

Airbus wants to step up the production rate of the A220 by 50% in 2024, with another increase in 2025.