Aircraft manufacturer Bombardier has won its case against US proposals to impose tariffs of 292% on its imports to America.
The move is expected to safeguard thousands of jobs in Belfast, where Bombardier’s C Series wings are manufactured.
The US International Trade Commission (ITC) said rival manufacturer Boeing did not suffer injury from Atlanta-based Delta Airlines' order of Bombardier's C Series passenger jets.
Bombardier said: "Today's decision is a victory for innovation, competition, and the rule of law.
"It is also a victory for US airlines and the US travelling public.
"The C Series is the most innovative and efficient new aircraft in a generation.
"Its development and production represent thousands of jobs in the United States, Canada, and the United Kingdom."
The decision comes after British Prime Minister Theresa May raised the issue with US President Donald Trump during a meeting at the World Economic Forum in Davos, Switzerland, on Thursday.
PM: I welcome this decision, which is good news for British industry. Bombardier and its innovative workforce play a vital role in the Northern Ireland economy.
— UK Prime Minister (@Number10gov) January 26, 2018
DUP MP for East Belfast Gavin Robinson said: "This is fantastic news for Bombardier and particularly for the firm's 4,000 workers in Northern Ireland and the many more who form part of the supply chain here.
"This has been a very difficult time for those staff who faced an uncertain future.
"Even in recent days there some pessimism had grown, but Bombardier's greatest strength here in Belfast is the quality of those workers and the product they deliver."
The ITC's role was to determine whether the aircraft manufacture industry in America was damaged by imports that the US administration believed were being sold too cheaply.
Bombardier has received large sums from government administrations in the UK and Canada as part of the development of the C Series.
It had argued the Commerce Department's tariff threat ignores long-standing business practices in the aerospace industry, including launch pricing and the financing of multibillion-dollar aircraft programmes.
But Boeing said its business was damaged because Bombardier received illegal government subsidies, dumping the C Series in the US through the cut-price 2016 Delta sale of 75 jets.
