Freak weather or something more? Why is Delhi seeing flight delays due to fog in Feb-end?

New Delhi: At least seven flights were diverted and many others were delayed after the Delhi airport. "Bad weather" and "Poor visibility" were blamed for the delayed takeoffs by SpiceJet and IndiGo on Wednesday.

"Due to dense Fog, flight operations at Delhi Airport may get affected. Passengers are requested to contact the airline concerned for updated flight information. Any inconvenience caused is deeply regretted," the latest update by the Delhi Airport's official Twitter handle read.

According to reports, the low visibility procedure was initiated at the airport from 6:30 AM on Wednesday. However, III CAT-equipped planes are allowed to operate, some news reports said. Sources said that the visibility is down to 70 meters at the airport, and a blanket of fog was witnessed around the airport.

Dense flog makes the taxiing of aircraft difficult. The airport switch to Low Visibility Procedures (LVPs) when the visibility drops below 600 metres. The pilots need to confirm that the plane is placed perfectly in the centre of the runway.

In order to ensure a safe distance between aircraft awaiting takeoff confirmation, the holding point on the taxiway where the planes await a signal to enter the runway is moved further away, the Business Standard said in a report. This ultimately causes delayed takeoffs.

An aircraft is not allowed to enter the runway before the one preceding it is fully airborne. On regular days, a few planes are allowed to line up and take off in succession. With the LVP imposed, this practice is stalled -- causing further delays.

Dense fog enveloped the national capital on Wednesday, with the Air Quality Index (AQI) continuing to be under the "poor" category for a second consecutive day.

According to the India Meteorological Department (IMD), visibility levels dropped to 50 metres at the Palam Observatory near the Indira Gandhi International Airport.

"A cyclonic circulation has developed over Punjab and Haryana under the influence of a western disturbance affecting the western Himalayan region. Warm and humid easterly winds and cool northwesterly winds are interacting over the region due to the induced cyclonic circulation. The increase in humidity and condensation is leading to fog formation. Such weather is not common in February," said Mahesh Palawat, a senior meteorologist at Skymet Weather.

Meanwhile, the overall AQI in Delhi was recorded at 201, according to data from the System of Air Quality and Weather Forecasting And Research (SAFAR).

Both the major pollutants PM 2.5 and PM 10 were recorded at 201 (poor) and 161 (moderate), respectively. The situation is expected to improve on Thursday morning, news agency ANI reported.