Delta Air Lines has confirmed a big order for 75 narrow-body Bombardier CS100 jets.
The carrier plans to fly the planes on short to medium-length routes once it starts taking delivery in 2018.
The deal is worth about $5.6 billion at list prices, although large orders of this volume usually get deep discounts.
Delta said the deal includes an option for a further 50 jets.
"The addition of Delta to our marquee CSeries customer list gives us tremendous momentum," said Bombardier CEO Alain Bellemare.
The big order could mark a turning point in the fortunes for the troubled C-Series project.
Development costs have run over budget and until a recent order from Air Canada ha struggle to secure a big deal from a major airline in North America.
Bellemare said the Delta order was a ‘game changer.’
"We are entering service with a strong tailwind," he said.
