Thousands of jobs at Bombardier's aircraft wing factory in Belfast are at risk as a feud between the Canadian-owned firm and US rival Boeing deepens.
Boeing alleged Bombardier had participated in anti-competitive practices with the sale of up to 125 of its C Series jets to Delta Air Lines. Boeing said the firm was "dumping" them on the US market by selling them below cost price and benefiting from subsidies.
Bombardier said its US rival's complaints were "pure hypocricy".
It said: "Boeing's self-serving actions threaten thousands of aerospace jobs around the world, including thousands of UK and US jobs and billions of purchases from the many UK and US suppliers who build components for the C Series."
The US International Trade Commission is expected to make its ruling public on Tuesday.
The trade court's ruling could endanger Bombardier's deal with Delta as the airline would have to pay duties on every C Series, and it could also hinder future sales.
Justin Trudeau, Canada's Prime Minister, last week said he would not confirm the country's purchase of 18 Super Hornet fighter jets from Boeing until the company backed down from its challenge against the Canadian giant.
Bombardier is Northern Ireland's largest manufacturing employer, and the factory, known as Short Brothers, employs around 4,200 staff.