Dense fog enveloped the airport here on Wednesday morning delaying over half a dozen domestic flights.

Seven morning flights to Amritsar, Mumbai, Leh, Chandigarh, Pune and Patna were delayed by upto one hour as the visibility at the runway dropped to 100 metres, airport sources said.

“The runway visibility hovered between 200 to 350 metres at around 8 am, leading to implementation of CAT-III instrument landing system,” Director of the Indira Gandhi International Airport MeT department R K Jenamani said.

The general visibility at the airport was recorded at 150 metres while the runway visibility of main runway (28/10) dipped to a low of 600 metres.

Also poor visibility conditions at Patna, Amritsar and other northern cities led to rescheduling of a few flights.

“Air India’s flight to Patna (IC 409), whose scheduled departure was at 7.05 am was rescheduled at 9.30 am as visibility at the airport there was poor,” an airlines official said.

Unlike last year, Delhi has not experienced any major flight disruption or diversion due to dense fog this time around.

Over 1,000 flights were delayed last season despite two CAT-III B compliant runways at the Delhi airport.

In an effort to reduce the number of flight delays and cancellations due to fog, the Civil Aviation Ministry and the Directorate General of Civil Aviation (DGCA) have asked the airlines to deploy their CAT-III B equipped aircrafts and roster their CAT-III B trained pilots.