Dense fog and near-zero visibility have once again thrown air travel across North India into disarray, with airlines issuing a series of fresh advisories for passengers flying through Delhi and other key cities.

As a thick winter fog settled over the region in recent days, early-morning and late-night flight banks have borne the brunt of disruption, triggering hundreds of delays and cancellations and prompting carriers to urge travelers to check their flight status before leaving for the airport.

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Dense fog grips Delhi and North India’s aviation hubs

Delhi’s Indira Gandhi International Airport has been at the epicenter of the latest spell of fog-related disruption, as visibility has repeatedly dropped below operational thresholds since mid-December.

On several mornings, visibility at key observation points such as Palam has fallen to 50 meters or less, forcing the airport to keep Low Visibility Procedures in force for extended periods and sharply curtailing movements during the busiest early-morning wave of departures and arrivals.

Authorities and airlines report that the worst impacts have been concentrated in the morning and late-night hours, when natural light is absent and fog tends to be densest and most persistent.

These time bands are typically used by carriers for high-density domestic and international banks, amplifying the knock-on effects when conditions deteriorate.

Once the sun rises and visibility improves, airports have raced to clear backlogs, but congestion and crew duty time limits have meant that normal operations often do not resume until well into the afternoon.

The weather pattern has not been confined to the capital. Dense to very dense fog has been reported across large swathes of Uttar Pradesh, Punjab, Haryana, Bihar and parts of Rajasthan, affecting airports in cities including Lucknow, Amritsar, Chandigarh, Varanasi, Patna and Jaipur.

The broad geographic spread of the fog has limited the ability of airlines to re-route or swap aircraft easily, with poor visibility impacting both origin and destination points on many key routes.

Hundreds of flights cancelled and delayed in a single day

The cumulative disruption this month has been stark. On multiple days, Delhi airport alone has recorded flight cancellations and delays on a scale more akin to a major storm than routine winter fog.

Around December 15, airport data and airline statements indicated that more than 220 flights were cancelled and several were diverted from the capital in a single day, amid plummeting visibility and severe air pollution that further degraded conditions.

In the days that followed, heavy fog continued to play havoc with schedules. On December 19 and 20, visibility again dropped sharply during the early morning hours, with aviation trackers and airport officials reporting well over 100 cancellations on consecutive days at Delhi, alongside several hundred delays.

Average delays for arriving flights stretched close to two hours during the worst of the disruption, with departures also facing extensive hold times on the ground.

The trend has persisted into the final week of December. On December 23 and 24, dense fog over Delhi and other North Indian cities led to dozens of additional cancellations and widespread delays.

At one point on December 23, flight tracking platforms recorded around 270 delays and at least 10 cancellations at Delhi as visibility fell below 100 meters.

A similar pattern played out on December 24 and 26, as repeated fog intrusions during the morning bank forced carriers to pare back their schedules and proactively cancel services that could not be operated safely or within workable connection windows.

Airlines issue fresh advisories as visibility slumps

India’s major carriers have responded by issuing a series of travel advisories, both general and city-specific, to alert passengers to the deteriorating conditions.

IndiGo, the country’s largest airline by market share, has over the past two weeks repeatedly warned customers via social media and direct messaging that dense fog in Delhi and other North Indian cities would lead to delays and cancellations across its network.

On several days, the airline proactively cancelled flights through the morning period to “ensure safe and compliant operations through the rest of the day,” while promising to inform impacted passengers through email, SMS and WhatsApp.

Air India has released its own advisories highlighting the risk of disruption at Delhi, Lucknow, Amritsar, Chandigarh and other fog-prone airports.

In a notice issued on December 27, the flag carrier cautioned travelers that dense fog and poor visibility could affect operations in multiple North Indian cities over the weekend, and urged passengers to verify their flight status on official channels before leaving for the airport.

The airline has also advised those with flexible plans to consider rebooking out of the most vulnerable time windows, particularly early morning departures.

Other carriers, including low-cost airline SpiceJet and regional operators, have echoed these warnings. SpiceJet has stressed that departures and arrivals to and from Delhi may be affected as long as low visibility persists, telling passengers that downstream flights on its network might also be impacted because of aircraft and crew rotations.

Several airlines have reminded travelers that they can change or cancel affected bookings without penalty in certain cases, particularly where the disruption is directly linked to adverse weather rather than internal operational constraints.

Morning and late-night banks hardest hit

The current pattern of disruption reflects both meteorological conditions and the structure of airline schedules at Delhi and other large hubs.

In winter, North India’s radiation fog tends to intensify just before dawn, when ground temperatures are at their lowest and moisture condenses rapidly near the surface.

This timing coincides almost exactly with the first major departure wave of the day, when airlines schedule a dense bank of flights between roughly 4:30 am and 9:00 am to feed business and connecting traffic.

When visibility plunges during this period, the combination of reduced runway capacity and tighter safety margins means that even modest schedule banks can quickly overwhelm available slots.

Flights ready for departure are held on the ground, arrivals stack up in holding patterns or are diverted, and stand availability is strained as aircraft cannot depart on time, leaving incoming flights without parking positions.

Airlines are then forced to triage, cancelling or combining services that have lower loads or weaker connectivity to free up slots and aircraft for priority routes.

Late-night and post-midnight banks, which have grown in importance as airlines chase higher aircraft utilization, face a similar vulnerability.

Fog formation often begins late in the evening and thickens overnight, catching late departures and incoming red-eye flights in rapidly worsening conditions.

This has led some carriers, especially low-cost operators with tight turnarounds, to pre-emptively cancel a selected number of late-night and very early morning services on days when forecasts indicate particularly dense fog, in an attempt to avoid cascading disruptions into the next operating day.

How India’s low-visibility systems are being tested

Delhi’s Indira Gandhi International Airport is equipped with advanced Category III Instrument Landing Systems, designed to allow suitably trained pilots and aircraft to land even when visibility is severely reduced.

Under ideal circumstances, these systems can support operations when the runway visual range drops to around 50 meters, a capability shared by only a handful of airports in the wider region.

Over the last decade, this infrastructure has significantly improved winter operational resilience, cutting down on the number of diversions and outright closures.

This fog season, however, conditions have at times pushed even these systems close to their limits. Episodes of near-zero surface visibility, compounded by extremely poor air quality, have created conditions in which safe operations cannot always be guaranteed even with full CAT III procedures in place.

In addition, not all airlines, aircraft types or individual flights are CAT III compliant, meaning that some services must be delayed or cancelled even when the runway remains technically available for certain operations.

Aviation experts note that while infrastructure like CAT III ILS and Runway Visual Range systems are critical, they are only one part of the safety chain.

Airlines must also ensure that crews are current on low-visibility procedures, that aircraft are appropriately equipped, and that contingency plans exist for diversions and holding patterns when congestion spikes.

The recent wave of disruptions has prompted renewed calls from passenger groups for clearer, more standardized communication from both airports and airlines about what low visibility procedures mean in practice and why certain flights can operate while others cannot.

Knock-on effects across rail and road networks

The heavy fog has not been an aviation problem alone. Rail operations into and out of Delhi and other North Indian hubs have also seen significant delays, with major express and premium trains running several hours behind schedule during the worst of the low-visibility spells.

For many long-distance travelers, the combined impact on air and rail has sharply reduced alternative options, particularly during the peak year-end holiday period when trains and buses are already heavily booked.

On key highways leading to Delhi airport, dense fog and poor air quality have slowed traffic to a crawl on multiple mornings, with police and traffic authorities advising motorists to use fog lights, reduce speed and avoid non-essential travel during the hours of lowest visibility.

While there have been no reports of major accidents directly affecting airport access roads during the latest wave, authorities warn that the risk of pile-ups rises sharply when drivers underestimate stopping distances in fog.

Transport planners say that the combination of delayed flights, late-running trains and slower road conditions has intensified the strain on airport terminals, as passengers arriving late for already delayed flights add to queues at check-in and security.

In some cases, travelers arriving by rail or intercity bus have missed their rebooked flights because connecting ground transport has been equally affected by the fog, leading to a compounding of individual travel disruptions even when headline flight operations appear to be stabilizing.

What travelers flying through Delhi and North India should expect

With meteorological forecasts indicating that dense to very dense fog is likely to persist in parts of North India over the coming days, airlines and aviation authorities are cautioning passengers to brace for continued disruption, particularly during early-morning and late-night operations.

Travelers with non-essential or flexible itineraries are being advised, where possible, to select mid-morning to early-evening departure windows, which statistically have a lower risk of fog-induced disruption at this time of year.

For those who must travel during the most exposed time bands, airlines emphasize the importance of monitoring flight status frequently through official websites, apps or customer service channels, rather than relying solely on static schedule information.

Many carriers are pushing real-time updates through SMS and messaging apps, but network congestion and outdated contact details can mean that not all passengers receive notifications in time.

Travelers are also being encouraged to allow extra time for airport transfers, given the impact of fog on road traffic speeds and potential congestion at terminal entry points.

In terms of passenger rights, policies differ by carrier, but weather-related disruptions are generally treated as circumstances beyond the airline’s control.

That means automatic compensation may not be available, though most airlines are offering free date or time changes in cases where flights have been cancelled or subject to major delays. Some full-service carriers are also providing meal vouchers or basic refreshments in the event of prolonged terminal waits, especially for elderly passengers or those traveling with young children.

Travel insurers, meanwhile, report a spike in claims related to missed connections and additional accommodation costs linked to the recent fog episodes.

FAQ

Q1. Why are flights in Delhi and North India facing so many delays and cancellations right now?
Dense winter fog and very low visibility, especially during the early-morning and late-night hours, are severely constraining runway operations at airports such as Delhi, Lucknow, Amritsar, Chandigarh and others. When visibility drops below certain thresholds, flights have to be slowed, spaced further apart, diverted or cancelled altogether for safety reasons.

Q2. Are all flights affected equally during foggy conditions?
No. The impact depends on the time of day, the specific airport, the equipment on the aircraft, and whether the airline and crew are certified for advanced low-visibility procedures. Morning and late-night banks are most exposed, and some flights may continue operating while others are delayed or cancelled, based on safety and operational constraints.

Q3. What are Low Visibility Procedures and CAT III operations that airlines keep mentioning?
Low Visibility Procedures are special operating protocols that airports and air traffic control implement when visibility drops, involving tighter control of ground movements and runway use. CAT III refers to advanced instrument landing systems that allow suitably equipped aircraft and trained pilots to land in very poor visibility. Even so, there are limits beyond which operations must be reduced or halted.

Q4. How can I find out if my flight is likely to be affected by fog?
The most reliable way is to monitor your flight status on your airline’s official website or app and keep an eye on local weather forecasts for your departure and arrival cities. If you are scheduled to fly in the early morning or late at night from a North Indian airport during this foggy period, the probability of disruption is higher than for midday or afternoon flights.

Q5. What should I do if my flight is cancelled due to dense fog?
Follow the instructions provided by your airline, which will typically offer free rebooking on the next available service or, in some cases, a refund. Avoid going to the airport before you have a confirmed alternative, as queues can be long and rebooking is often more efficient via digital channels or call centers during widespread weather disruptions.

Q6. Am I entitled to compensation if my flight is delayed or cancelled because of weather?
In most jurisdictions, including India, weather-related disruptions such as dense fog are treated as extraordinary circumstances beyond the airline’s control. That usually means statutory compensation is not mandated. However, airlines often provide waivers for change fees, may offer refunds for cancelled flights, and sometimes provide meals or basic refreshments during long waits as a goodwill measure.

Q7. Is it safer to book midday flights during the North Indian winter?
From a disruption perspective, midday and early-afternoon flights generally face a lower risk of fog-related delays because visibility usually improves once the sun is higher and ground temperatures rise. While no time slot is completely immune to disruption, choosing flights outside the peak fog hours of early morning and late night can reduce the likelihood of major schedule changes.

Q8. Why can some planes land in fog while others cannot?
Not all aircraft and operators are equipped or certified to use the most advanced instrument landing systems. To conduct CAT III operations, both the aircraft and the flight crew must meet specific technical and training requirements. Flights that do not meet those standards may have to divert or wait until visibility improves, even if the runway is open for better-equipped services.

Q9. How long is this period of dense fog expected to last in North India?
Meteorologists typically expect dense radiation fog in North India to recur through much of late December and January, with intensity varying from day to day. Current outlooks suggest that dense to very dense fog could persist on multiple mornings over the coming days, particularly across Delhi, Uttar Pradesh, Punjab, Haryana and Bihar, so intermittent disruption is likely to continue.

Q10. What practical steps can travelers take to reduce inconvenience during this fog season?
Travelers can try to book flights outside the most vulnerable fog windows where possible, monitor flight status closely, allow extra time for travel to the airport, keep contact details updated with their airline, and consider travel insurance that covers weather-related delays. Carrying essential medicines, snacks, and chargers in hand baggage can also make prolonged waits in terminals more manageable if disruption occurs.