The US Commerce Department is to publish its findings in a trade dispute which could threaten thousands of jobs in Northern Ireland on Tuesday. Here are some key questions.
:: What is the row about?
It centres on US-based Boeing's allegations that Canadian-headquartered Bombardier received state subsidies allowing it to sell its C-Series planes at below-market prices in America.
If that view is substantiated by the authorities in Washington then officially-imposed tariffs could increase the cost of selling into one of the world's most important aviation markets.
Bombardier is contracted to supply up to 125 C-Series aircraft to Atlanta-based Delta Airlines in a deal underpinning many staff posts at its manufacturing plant in Belfast.
The UK Government has been actively lobbying in the US for a compromise between Boeing and Bombardier amid growing concern about the potential implications for Bombardier's Northern Ireland operations.
:: What are the aerospace companies saying about it?
Boeing submitted a petition with the US International Trade Commission and the Department of Commerce in April which claimed large government subsidies helped Bombardier launch an aggressive campaign to "dump" its C-Series aircraft in the US.
It said there was a shared industry interest in a level playing field.
Bombardier has repeatedly rejected Boeing's claims, accusing its rival of pure hypocrisy after it alleged anti-competition practices in the sale of aircraft.
"Bombardier shares Boeing's commitment to a level playing field, but in this case, they were not even on the field."
:: What are the implications for Belfast?
Bombardier had been under financial pressure and invested large sums in its new jet programme, which is crucial to many jobs in the city.
Last year the firm announced 1,080 job losses at its Northern Ireland plants following delays to the C-Series.
It is one of the country's largest employers, with around 4,500 on the books, and supports hundreds of other jobs through its suppliers.
:: What is the Government doing about it?
:: Political powersharing at Stormont has been in cold storage for months. However the DUP's 10 anti-Brexit MPs are a crucial force propping up the Government in key votes after Theresa May lost her majority in this year's General Election.
DUP leader Arlene Foster's influence has seen the Prime Minister lobbying US President Donald Trump during a recent visit to New York.