European planemaker Airbus signed a deal with Qatar Airways for 80 A350XWB aircraft with a total list price of $16 billion.
The order replaces a 2005 agreement for 60 planes.
A memorandum of understanding was signed at the Elysee palace in the presence of French President Nicolas Sarkozy and the Emir of Qatar, Sheikh Hamad bin Khalifa al-Thani.
The aircraft include 20 A350-800, 40 A350-900 and 20 A350-1000. Deliveries will begin from 2013.
"The A350XWB will equip Qatar Airways with the very latest generation and most modern fleet," Qatar Airways Chief Executive Officer Akbar al-Baker.
A spokeswoman for Qatar Airways in Qatar said the terms for buying the Airbus aircraft would be agreed by the time of the Paris air show next month.
Airbus President and Chief Executive Officer Louis Gallois, also co-Chief Executive at parent group EADS, told Reuters the order was unrelated to a possible decision by Qatar to take a stake in EADS.
Gallois said these discussions were taking place with EADS shareholders. He denied newspaper reports that clients were asking for changes to the A350 plane.
"Nobody asked us to change the plane, which will be made of composite materials for a little bit more than 50%," he said.
Qatar Airways is the largest all-Airbus operator in the Middle East and is also a customer for the A380 super jumbo which has hit delivery delays. Qatar had indicated it wanted compensation from Airbus for the delay in the A380, for which it had two firm orders and two options.
"Qatar will be the first to get a A350, in mid-2013," Gallois told Reuters.
Gallois slammed recent newspaper reports about alleged new problems at the planemaker, based in Toulouse in the south of France, which plans to cut thousands of jobs to slash costs.
"All this talk in the media everyday about delays to the A380, the consequences, that's history," he said.
"I find the focus on these issues gigantic at a time that there are 120,000 people who work at EADS, that sell products and are working on development," he said.
"At Airbus we had problems. But the A380, we will deliver the first planes on time, we will step up the pace of deliveries of all planes," Gallois said.
"The development of the A350 is taking place in good conditions, in line with our engagement," he said.
EADS shares remained down in Paris but above lows, trading 1.12% easier at 22.98 euros at 1158 GMT while it had earlier set a low at 22.74 euros amid newspaper reports on a probe by the AMF French financial watchdog about alleged insider dealing. EADS co-chairman Arnaud Lagardere was questioned by the AMF on Tuesday and newspapers said he denied any wrongdoing.