BELFAST, July 1 (Reuters) - Politicians raised concerns on Monday about jobs not secured in Airbus' takeover of the bulk of production at Spirit AeroSystems plant in Belfast, one of Northern Ireland's biggest employers.

Airbus' move to take control of the core activities at four Spirit plants, including in Belfast where the fuselage supplier employs around 3,600 people, was part of Boeing's $4.7 billion deal on Monday to buy back Spirit.

Located yards from the shipyard that built the Titanic in East Belfast, the plant is by far the most important manufacturer left in the capital city, once one of the key industrial centres of the British empire.

While most of Spirit's Belfast production is on Airbus jets, the Unite trade union, which represents the majority of Spirit workers across the United Kingdom, has said around 40% of the jobs there are tied to lines for other air manufacturers including Bombardier and Rolls Royce.

Spirit plans to sell the parts of the factory that do not support the Airbus manufacturing programmes separately. The Airbus deal is subject to due diligence, which the planemaker said it would complete in as timely a manner as possible.

The leader of Northern Ireland's largest unionist party, the Democratic Unionist Party's (DUP) Gavin Robinson, said the sale represented only "a partial solution".

The plant - which Spirit bought from Bombardier in 2020 when staff were caught in the crosshairs of a far-off trade war - has been a pillar of Belfast's economy for decades. Unite estimates that a further 7,000 job across Northern Ireland depend on supplying the plant.

Originally owned by Short Brothers, the world's oldest planemaker, the site is of particular significance to the region's mainly protestant unionist community who long provided the vast majority of workers at Shorts and the neighbouring Harland & Wolff shipyards, which built the Titanic.

Steve Aiken, a member of the smaller Ulster Unionist Party, said it was an outcome "neither management, workforce or the unions desired", calling on Northern Ireland's economy minister to intervene to ensure the entire business is retained.

"The minister also needs to emphasis to Airbus the considerable investment the Northern Irish and UK governments have made in wing and aerostructure manufacturing in Belfast and that we will not be allowing our aircraft industry to be asset stripped and manufacturing moved elsewhere," Aiken added.

Economy Minister Conor Murphy said in a statement that he was engaging with all involved to ensure workers are protected. (Reporting by Amanda Ferguson, writing by Padraic Halpin; editing by Jason Neely)