Delhi airport is seeing flight delays and cancellations. (ANI photo)

NEW DELHI: Dense fog blanketed Delhi and large parts of North India on Monday, triggering widespread disruption across air and rail networks, with hundreds of flights cancelled or delayed and trains running hours behind schedule, leaving passengers stranded and frustrated.At the Indira Gandhi International (IGI) Airport, at least 128 flights — 64 departures and 64 arrivals — were cancelled, while eight flights were diverted due to low visibility conditions. Nearly 200 flights were delayed, with an average departure delay of around 24 minutes, according to flight-tracking website Flightradar24.

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Visibility at the airport dropped to as low as 50 metres, forcing operations to continue under CAT III conditions, an advanced landing system used during dense fog.

Delhi's AQI also crossed 400 on Monday, hitting 'severe' category of air pollution.Delhi International Airport Ltd (DIAL) said runway visibility was gradually improving but warned that departures and arrivals could remain affected.IndiGo cancelled 80 flights across its network due to bad weather, with around half of those cancellations at Delhi airport. Other affected airports included Mumbai, Bengaluru, Kochi, Hyderabad, Kolkata, Amritsar, Chandigarh, Jaipur, Dehradun, Indore, Patna and Bhopal.

While the airline did not explicitly disclose the number of cancellations in its advisory, it acknowledged that fog-related disruptions were likely to extend into the afternoon hours.“Fog continues to persist across Delhi and several airports in northern India. Visibility remains reduced and, as a result, flight movements are presently slower than normal,” IndiGo said in a post on X.

The airline has been cancelling flights in significant numbers since the start of the fog season on December 10, following earlier large-scale disruptions caused by stricter pilot duty norms.

The Directorate General of Civil Aviation (DGCA) has designated December 10 to February 10 as the official fog window this winter, during which airlines must deploy CAT-IIIB-compliant aircraft and pilots trained for low-visibility operations.Airlines including IndiGo and Air India urged passengers to regularly check flight status and assured them that safety remained the top priority as operations continued to adjust to fluctuating weather conditions.Rail services hitRail services were also hit hard. Several trains were delayed by hours at New Delhi and Hazrat Nizamuddin railway stations, prompting passenger complaints. Gagan, travelling to Kanpur, told ANI that his train was delayed by eight hours, while students expressed concern about missing meals, exams and connections due to prolonged delays. Taxi drivers at stations reported a sharp drop in business as late-arriving trains reduced passenger movement.The fog also raised safety concerns on roads, with commuters warning of increased accident risks due to poor visibility. Meanwhile, smog reduced visibility in parts of Mumbai, adding to travel woes.