Airbus has reached a deal for a majority stake in Bombardier's C-Series planes - which could avoid new US import tariffs slapped on them.
It comes after weeks of uncertainty for workers in Belfast who make the jets' wings.
The deal still needs approval by regulators.
The Unite union said the deal should safeguard the production jobs in Belfast "for the foreseeable future" - but stressed there were "continued challenges" over jobs linked to other Bombardier contracts in Belfast.
Business journalist Vincent Wall says the deal is a significant development, saying Bombardier is a 'huge employer' in Belfast.
DUP leader Arlene Foster hailed the announcement as "incredibly significant" news for Belfast and Northern Ireland.
She said: "Having personally supported the aircraft through its development, I'm thrilled there is a bright future ahead following what has been a dark time for staff and management.
"I hope this will safeguard the C Series programme."
