As many as 450 flights were affected at the Indira Gandhi International Airport due to dense fog in Delhi on Friday morning.
The flight operations remained disrupted between 5.30 am and 1 pm.
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"Around 97 per cent of these 450 flights were either departing or arriving beyond their scheduled time due to dense fog that remained till around 10.20am. Rest were either diverted or cancelled," an official said.
Another official said departures were largely put on hold between 5.30am and 10.20am. Arrivals were happening only intermittently between 6am and 7.20am, he said.
Five flights were diverted between 5.30am and 10.20am from the airport. One of the flights was coming from Singapore and it was diverted to Kolkata, he said.
Four flights — coming from Bangkok, Dubai, Guwahati and Muscat, respectively — were diverted to Jaipur between 7.30am and 10.20am, he said.
"Very few aircraft are departing and that too on the basis of their size, visibility and ATC (air traffic control) clearance for taking off," the official said.
At the Delhi airport, the minimum runway visibility required to take off is 125 metres.
The airport was facing low visibility conditions since 4am due to dense fog.
"The visibility significantly improved between 9.20am and 10.20am. This allowed us to resume departures properly from 10.20am onward," he said.
Vistara Airlines tweeted at 8.23am, "Due to dense fog and poor visibility in Delhi, delays are expected for both arrivals and departures with likely consequential impact on flights across the network."
"Currently, flight departures from Delhi are on hold and will resume by 0930 hrs subject to weather clearance," it added.
Jet Airways tweeted at 6.33am that some of its flights had been affected due to dense fog at Delhi and Bengaluru airports.
(With PTI inputs)