Flights delayed by pollution

Around the world most of the discourse on the connection between air pollution and aviation is about how much carbon emissions airliners give off. But in Nepal, the more recent trend is that poor visibility due to ground-level air pollution is affecting aviation.

The whole of March and part of April, Nepal was blanketed by thick smoke from forest fires. In winter, Kathmandu Valley becomes a cauldron of pollution. In autumn, crop residue burning in India is mixed with industrial and vehicular emissions which prevailing winds blow towards the mountains.

Air pollution closed down Pokhara airport for several days in late March. International airlines have cited poor visibility as one of the reasons they have decided not to operate flights to Bhairawa. And in Kathmandu, poor runway visibility has led to chronic delays for the past months.

Kathmandu airport is already congested with more than 80 international flights and 250 domestic movements to and from domestic destinations daily. When surface visibility is below 1,500m, the airport is closed and only if the visibility is more than 5,000m do Visual Flight Rules (VFR) apply. 

Most mornings for the part months, the visibility is too low and planes are allowed to land only under Instrument Flying Rules (IFR) which means long holding patterns for pilots to queue up in the air before making an approach into Kathmandu.

Kathmandu ranked number 1 among capital cities in the world for Air Quality Index (AQI) according to rankings by IQAir. This was due to the rise in wildfires caused by prolonged winter drought, vehicle emissions, and transboundary pollution blowing in from India.

The poor visibility in Pokhara has already affected tourism, with travel operators citing recent cancellations of bookings due to the mountains not being visible. Overall, the impact of international publicity about air pollution in Nepal has had a negative impact. 

The visibility of Kathmandu airport is affected by its location in a valley, where fog and haze can significantly reduce visibility, especially in winter. While the visibility of Pokhara airport can vary it was severely affected by wildfires in Central Nepal in March. Tumlingtar airport was also closed for several days last month because smoke from forest fires reduced visibility. 

Buddha Air, which flies to most of these airports, says that poor visibility and resulting congestion has been the reason for most delays for the past months. When flights into Kathmandu in the morning are delayed, it has a domino effect throughout the day. For most of April, the congestion was made worse because Kathmandu airport’s operation time was reduced to 14 hours a day due to runway and taxiway upgrading work.

When planes have to hold for a long time in the air to land and wait in the taxiway to takeoff, they also burn more fuel, and add to the pollution in the air. Studies of Kathmandu Airport

reveal that aircraft operations emit between 898 to 2,123 tonnes of pollutants annually, including nitrogen oxides (NOₓ), carbon monoxide (CO), and particulate matter. These emissions predominantly occur during taxiing and idling phases, underscoring the need for sustainable aviation practices.

Nepal’s largest domestic airline, Buddha Air, for example has incorporated eco-friendly initiatives to mitigate its environmental footprint. Since 2008, the airline has integrated fuel-efficient ATR 72 aircraft into its fleet, these turboprops consume up to 45% less fuel than other planes of similar capacity.