The Rolls-Royce support announced in the Budget is for a £2.5bn programme to develop jet engines for narrowbody aircraft, and the taxpayer is understood to be covering £1.25bn of it, BM Magazine reports.
The Chancellor, John Healey, announced the government's backing in his statement. The key points published on Budget day gave no figures.
The government says the programme supports 3,300 UK jobs. That claim has not been independently checked.
The government said the funding is subject to legal, value-for-money, affordability and approval processes. Rolls-Royce said the plan remains subject to a final agreement. It did not say how the cost is split, so the £1.25bn taxpayer share has not been confirmed by the company.
Rolls-Royce said it expects to invest significantly more than the government across its wider narrowbody programme.
The FT had reported before the Budget that a subsidy deal was close, according to Reuters.