Turkish Airlines will buy more than 200 Airbus planes - with an option for more than 100 more - over the next decade as it aims to become the world's largest carrier.
Turkish Airlines CEO Bilal Eksi said in a statement on social media that the entire order could potentially reach 355 aircraft.
The deal will be one of the largest in the industry and will significantly expand the Turkish company's existing fleet of 439 aircraft.
"I wish luck to our country and our company," Exy said.
The purchases will be made as part of the company's "strategic plan" for 2023-2033.
The airline's confirmed order – which includes 150 A321 NEOs and 60 wide-body A350-900s – has a price tag of more than $40 billion.
The Turkish carrier's existing fleet is split evenly between Airbus and Boeing aircraft.
The new order gives the European aerospace giant a huge boost in its race for global supremacy with its American rival.
"This latest generation aircraft order is a demonstration of Turkish Airlines' bold vision," Airbus CEO Christian Scherer said in a statement.
"We are proud to accompany Turkey's connection with the world with our most advanced aircraft," he added.
Turkish Airlines is based at the newly built Istanbul International Airport and flies to 120 countries.
The company claims it holds "the title of the airline that flies to the most countries in the world".
The deal also includes a separate order for Rolls-Royce to provide maintenance services and spare parts for the A350 aircraft engines.
According to the British government, 70 of the newly purchased aircraft will be powered by Rolls-Royce.
"This landmark deal between Turkish Airlines, Airbus and Rolls-Royce demonstrates that the sky is the limit for the UK's thriving aerospace sector," said British Prime Minister Rishi Sunak.
British Trade Secretary Kemmy Badenoch called the deal "a victory in the bidding for the UK's world-leading space sector". /BGNES