QRadio News
The UK Government needs to stand up for Bombardier jobs, manufacturers in Northern Ireland said.
Thousands of Belfast posts hang in the balance if a proposed 300% duty on exports to the US is imposed on the Canadian-owned firm's new C-Series jet.
Airbus has acquired a majority stake in the C Series in an arrangement which could see them avoid tariffs.
Stephen Kelly, chief executive of Manufacturing NI, said thousands of posts may be at risk.
"The UK needs to stand up for all those jobs, whether they are Boeing jobs or Bombardier jobs."
He told the Northern Ireland Affairs Committee of MPs: "Because of Airbus as well, the partnership makes it more important that the UK Government becomes more robust with Boeing as a company."
Production of the C-Series will be extended to the US state of Alabama, which bosses from European firm Airbus and Bombardier believe will mean it avoids import tariffs.
Airbus chief executive Tom Enders said planes built in the US would not be subject to duties under the US investigation.
But US aerospace giant Boeing has said it looked like a questionable deal between two heavily state-subsidised competitors to skirt the recent findings of the US government.
Earlier this year the US Department of Commerce announced it would impose an interim tariff of nearly 220% on the jets - with unions warning the move could cost jobs in Belfast.
A second preliminary levy of 80% has been loaded on sales of the Bombardier aircraft.
Announcing the regulator's preliminary finding, US Secretary of Commerce Wilbur Ross said the subsidisation of goods by foreign governments was something that President Donald Trump's administration "takes very seriously".
Bombardier labelled the determination "absurd", while in its response the UK Government said the statement was "disappointing" and pledged to defend British interests "at the very highest levels".