Dense fog has enveloped Delhi-NCR, leading to the Air Quality Index (AQI) reaching the 'severe' category. The Indira Gandhi International Airport has issued travel advisories due to low visibility procedures, warning of potential flight disruptions including delays, diversions, or cancellations. Airlines like Air India and SpiceJet have also alerted passengers about possible impacts on flight operations. The city's AQI was recorded at 404, indicating severe air pollution levels.