Dense fog disrupted flight operations at the IGI Airport in New Delhi on Wednesday morning with 30 flights delayed and three cancelled. Two other flights were diverted.

The fog started to descend at the airport in the wee hours due to which the runway visibility dipped below 100 metre and the general visibility to less than 50 metre, an airport official said.

As the runway visibility was less than the required minima for takeoff of 125 metre and 150 metre, flights were unable to take off, he said.

However, flights arriving at the airport were landing using CAT-IIIB instrument landing system.

Two Jet Air flights arriving in New Delhi between 4 a.m. and 5 a.m. were diverted due to operational reasons.

According to sources, the pilots were not trained to operate CAT-IIIB landing system.

Due to poor visibility at the new runway, it was not operational and only the main runway was functional, the official said.

This is the first spell of dense fog this year.