A European airline intends to buy at least 31 of Bombardier's C-Series planes, the aerospace firm has said.
The unnamed airline has signed a letter of intent for 31 orders, with options for 30 more. It expects the deal to be agreed by the year's end.
C-Series wings are made at Bombardier's Belfast operation, providing employment for about 1,000 people.
For the third quarter of 2017, Bombardier posted a net loss of $117m on turnover of $3.8bn.
Alain Bellemare, Bombardier's chief executive, said: "This significant new order confirms the increasing confidence customers have in the C Series."
Based on the list price, a firm order would be valued at approximately $2.4bn (£1.81bn), rising to nearly $4.8bn should all 30 options be exercised.
Last month, Airbus agreed to take a majority stake in the C-Series project.
Bombardier has faced a series of problems over the plane, most recently a trade dispute in the US that imposed a 300% import tariff.
Bombardier was accused of anti-competitive practices by rival Boeing, which complained to the US authorities.
Boeing accused the Canadian firm of selling the jets below cost price after taking state subsidies from Canada and the UK.
Bombardier said it would fight the "absurd" import tariff ruling.
Gavin Robinson MP, whose constituency houses the Belfast plant, said the new orders were a "welcome piece of news for the company as a whole".
"The timing too is significant and is a vote of confidence in the joint venture between Bombardier and Airbus," he added.