Turkish Airlines is still working out the contours of its planned 600-aircraft order, with an announcement of the massive deal unlikely before the Paris Air Show in mid-June or even later, according to a person familiar with the matter.

Turkey’s national flag carrier is hammering out the mix of aircraft it needs and the engines that will power the planes it expects to use over the next decade as it targets a doubling of its passenger count, said the person, asking not to be identified as the discussions are confidential. Turkish may not split the order equally between Boeing Co. and Airbus SE, as it targets 400 narrowbody jets and 200 long-haul aircraft, the person said.

Last month, Turkish Airlines Chairman Ahmet Bolat said that part of the order will go to Boeing and will be announced during the annual meeting of the International Air Transport Association that is taking place in Istanbul next week.

Turkish Airlines declined to comment, as did spokespeople at Boeing and Airbus.

Turkish Airlines plans to double its fleet to 814 and passengers carried to 171 million as part of its strategic plan through 2033 as it takes on Middle Eastern behemoths Emirates and Qatar Airways for a bigger slice of inter-continental passenger flows. An order in the magnitude of 600 aircraft would be among the biggest ever unveiled, though the carrier would use a big portion of the jets to replace parts of an aging fleet.

Airlines around the world are moving quickly to lock in delivery slots with aircraft manufacturers, as they build up their fleets in a bet that the post-pandemic recovery is here to stay. Ryanair Holdings Plc recently purchased as many as 300 narrow-body jets from Boeing. In February, Air India Ltd split a major order for some 470 planes between the two competing manufacturers.

--With assistance from Selcan Hacaoglu.