Istanbul's new airport, which aims to become one of the world's busiest, will not become fully operational until April 7.

The $12 billion project was declared open in October by President Tayyip Erdogan but only a handful of flights have been operating from the site since then.

Istanbul Airport will be able to handle 90 million passengers a year, and can be expanded to accommodate as many as 200 million, Erdogan said at the opening ceremony.

Its full operation had been delayed first until January and later pushed back to March, in a setback for the government which has hailed it as a centrepiece of the construction boom that has driven strong economic growth under Erdogan's 15-year rule.

The transfer to the new airport from the existing Ataturk Airport will begin on April 5 at 3am and will last 45 hours.

IGA, the company building and operating the airport, said it would announce recent developments on its website soon. 

The General Directorate of State Airport Authorities said it had not received information regarding the latest delay.