Kolkata, Jan 14 (Agencies): Heavy fog in Kolkata on Friday morning disrupted air operations at the airport with no flight being able to take off or land.

Authorities at the Netaji Subhas Bose International Airport said no flights have taken off from 5 am as the fog density was 50 metre leading to very low visibility.

Approximately 40 morning flights could not take off and about 13 in-coming flights could not land at the airport.

The New Delhi-Kolkata flight could not land and returned to New Delhi while the Kolkata-New Delhi Air India flight at 7 am  was cancelled and combined with the next flight of the airlines at 10 am, sources said.