At least 800 jobs in the city are reliant on manufacture of wings for the aerospace firm's C-Series aircraft but the workforce is "hardened" to the threat, according to employees.
They spent much of Tuesday "holding their breath" ahead of US authorities' findings.
Employee Marty Higgins said: "Of course people are worried about redundancies, people are always worried about redundancies when you work for this company."
He was just returning from his lunch break to the mammoth factory which employs more than 4,000 people on an industrial estate in Belfast Harbour.
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The harbour was once a thriving centre of heavy industry of all sorts - the Titanic ocean liner was built there - but Bombardier is one of the last remaining large manufacturing employers.
The work involves assembling state-of-the-art composite wings which help make the C-Series one of the most fuel efficient aircraft in the skies.
Mr Higgins added: "Not for a second would I think that Bombardier would have done anything wrong."
The C-Series planes are at the centre of an international trade dispute which threatens to inflict significant financial penalties on the company and the uncertainty has left some workers fearing for the future.
Ryan McNeil said: "People are concerned but I think it's just a case of waiting to see what the judgment is going to be. There's just no point in panicking.
"In this industry, people are used to things like this. There is some concern about it but the workforce is hardened to it and has been for a couple of years, I don't think we're panicking.
"I think what concerns people more is that this decision is being taken in America rather than on a global platform. So it's sort of out of our hands at the minute."
Bombardier has taken on and shed jobs for decades but the factory has been the backbone of thousands of livelihoods across Northern Ireland.
Unite assistant general secretary Tony Burke said: "Workers in Belfast are holding their breath."
Another staff member, who spoke on condition of anonymity, said: "People are scared about what will happen now. We don't know if people could lose their jobs, or just what is next."