Delhi woke up shrouded in dense fog on Wednesday, causing widespread disruption at the city’s Indira Gandhi International Airport (IGIA) and keeping air quality in the 'very poor' category.

At least 148 flights were cancelled and over 150 delayed at IGIA due to low visibility, officials said.

Two flights were diverted, while 78 arrivals and 70 departures were called off at the airport, which is operated by Delhi International Airport Ltd (DIAL). IGIA handles around 1,300 flight movements daily.

In a post on X, Indigo said, "Foggy conditions remain in place across Delhi and several airports in northern India, with visibility yet to improve fully. As a result, the earlier impact on flight movements is likely to extend into the noon hours, and some delays may continue."

The airline added, "We assure you that flight departures and arrivals are being sequenced to ensure steady and orderly movement, while keeping your journey and comfort in mind. Our airport teams are present at key touchpoints and right here to assist, should you require any support along the way. Thank you sincerely for your patience and understanding, and we wish you a comfortable and pleasant journey ahead. For flight status, please visit http://bit.ly/3ZWAQXd."

DIAL also posted that visibility at the airport is improving but cautioned that some flights may still be affected.

"Please be assured that our on-ground officials are working closely with all stakeholders to assist passengers and provide necessary support across terminals. Passengers are requested to contact the concerned airline for updated flight information," the airport said in a 10 am advisory.

The Ministry of Civil Aviation noted that prevailing fog in parts of Northern India could affect flight operations at select airports.

"Passengers are encouraged to remain updated through official airline channels and allow extra time for airport procedures," it said.

The ministry added, "Airlines have been instructed to strictly adhere to passenger service norms, including timely information, assistance during delays, rebooking or refunds where applicable, and baggage facilitation. Passenger safety and convenience remain the Ministry of Civil Aviation’s top priority."

The Airports Authority of India (AAI) also highlighted the impact of low visibility. "Low visibility due to dense fog is affecting operations at a few airports across Northern India, which may result in flight delays. Passengers are advised to track flight updates directly with their airlines and arrive at the airport earlier than usual. AAI teams are on ground at airports to assist passengers and ensure safe, smooth operations," it said.

Air India shared a detailed advisory late Tuesday night, saying, "Due to forecasts of dense fog and low visibility across Delhi and Northern India tomorrow morning, we anticipate impacts on flight schedules and potential cascading delays across our network. We are keeping a close eye on the situation and have taken proactive measures to minimise inconvenience to our passengers. This includes planned cancellation of some morning flights most likely to be affected by fog with advance information to passengers to avoid prolonged and uncertain wait at the airports."

The airline added, "In the event of any unexpected delay, diversion or cancellation of flights, our airport teams will remain at your service to extend necessary assistance and support. To give you more control over your travel, our FogCare initiative allows passengers booked on certain flights during the fog window, which may be affected, to receive advance alerts on their registered phone numbers, offering the option to reschedule their flights without any additional payment or seek a full refund on their bookings without penalty."

Air India advised passengers, "If you are scheduled to fly with us tomorrow, we request you to check your latest flight status here: https://airindia.com/in/en/manage/flight-status.html before proceeding to the airport and allow a wider window for your journey to the airport. Our contact centre is available round-the-clock at +91 11 69329333 / +91 11 69329999 for any assistance. We sincerely regret the inconvenience caused by these weather disruptions and appreciate your patience during these weather-related disruptions. The safety and well-being of our guests and crew are our absolute priority."

Alongside flight disruptions, Delhi’s air quality remained hazardous. The Central Pollution Control Board (CPCB) recorded a 24-hour average Air Quality Index (AQI) of 384. A station-wise breakdown showed 21 monitoring stations in the 'very poor' category and 16 in the 'severe' category, with Anand Vihar registering the worst AQI at 452. According to CPCB standards, AQI above 400 is considered 'severe.'

The India Meteorological Department (IMD) issued an orange alert for dense fog between 8.30 am and 10 am. Visibility at 6.30 am was just 50 metres at both Palam and Safdarjung. Officials attributed poor air quality to an unfavourable ventilation index below 6,000 square metres per second and low wind speeds of less than 10 kmph, conditions that prevent the dispersion of pollutants.

The IMD reported minimum temperatures of 6.4 degrees Celsius at Safdarjung and Ayanagar, slightly below normal, with maximum temperatures expected to reach around 23 degrees Celsius. Palam logged a minimum of 7.7 degrees Celsius, Lodhi Road 6.8 degrees, and the Ridge 7.8 degrees. Dense fog is expected to persist throughout the day, while the AQI may deteriorate to 'severe' on January 1 before easing to 'very poor' on January 2. The forecast for New Year’s Day predicts a generally cloudy sky with light rain over the capital.