Dense fog made a comeback at Delhi's Indira Gandhi International Airport (IGIA) and affected over 100 flights from midnight till early morning on Tuesday.
According to officials of Delhi International Airport Limited (DIAL), fog started covering the airport at 1:30am and operations were suspended at runway 29 for nearly four hours.
"Operations were suspended at runway 29 from 1:45am to 5am. Runway 28 was being used for operations during that time. Four flights were diverted, 37 were cancelled and over 50 were delayed," an airport source said.
"This season, the month of December had around six days of CAT-III dense fog that lasted for 46 hours. In totality, the first 22 days of December 2012 were completely fog-free, even without shallow fog or smog with mostly visibility above 1000m, which is unusual," a MET department official said.
Dense fog is expected to affect flight operations again on Wednesday and the weekend is likely to be worse as long hours of dense fog are predicted.
"The visibility was fluctuating from 150 m to 225 m at runway 28 from 1:30am to 9:30am, while at runway 29, the visibility was fluctuating from 50m to150m. But most of the time the visibility was below 50m," he added.
Dense fog also affected train operations, as Northern railway on Tuesday cancelled 13 trains and rescheduled another 18. Over two dozen trains were running late and some of them were late by 29 hours.
According to an air traffic controller, "During normal time, Delhi airport can handle 75 flight movements per hour but in fog season the capacity decreases.”