Around 80 domestic and international flights were delayed causing inconvenience to score of travellers.
An airport official, "Since last night 27 domestic and international flights were diverted, 18 were cancelled and around 20 have been rescheduled."
Some of the morning flights were delayed by over two to three hours while a few operated using the CAT-III B instrument landing system.
The runway visibility remained around 150 metres throughout the night due to which international flights, which were scheduled to depart last night and early this morning, were worst hit.
According to Met department, "This Jan is witnessing the worst fog of the past seven years."
The Met department said the last time the Delhi airport had seen such a long spell of fog was in Jan 2003.