Boeing's grounded 737 Max jet received a boost on Tuesday after British Airways-owner IAG signed a letter of intent to order 200 of the planes and said it was confident that it would return to service in the coming months.
Boeing said the deal had a value of more than $24 billion at list prices.
IAG said the mix of 737-8 and 737-10 aircraft, to be delivered between 2023 and 2027, would be powered by CFM Leap engines and used across a number of its airlines including British Airways, Vueling and Level.
The 737 Max was grounded in March following two deadly crashes, and Boeing has been working on a software fix to get the jet back flying by the end of the year.
IAG Chief Executive Willie Walsh said he had experienced Boeing's MCAS anti-stall software in person, adding it was "very helpful to see it in operation" and to "understand the changes" that Boeing was proposing.
"It gave me confidence both in terms of the aircraft and the changes that Boeing introduced," he said at the announcement of the deal at the Paris Airshow.
"I am confident in Boeing."
Boeing shares rose 2 percent on the announcement. The company is working towards a certification flight with regulators soon.
Boeing commercial airplanes boss Kevin McAllister said the decision of when the Max flies again was in the hands of the regulators.