Three international and nearly three dozen of domestic flights were cancelled on Friday after Kathmandu’s Tribhuvan International Airport experienced multiple problems, ranging from power outages and the failure of a backup system to a thick blanket of fog over the city.

The airport, which was closed down at 12 noon, resumed operations after 5pm, according to the airport authority.

The combination of these events underscores the vulnerability of critical infrastructure at the country’s only international airport, especially when there is inclement weather.

Air China, Qatar Airways and Sichuan Airlines flights were cancelled, the airport authority said.

Nearly a dozen of international flights, including Nepal Airlines, were forced to divert due to poor weather conditions.

“Some of the diverted planes have landed and some are waiting to land at the airport,” according to a terminal duty officer at the airport.

“The power failure brought the country's busiest airport to a standstill, but the more serious issue was that the backup power system did not work for more than 25 minutes,” an official at the airport told the Post on the condition of anonymity. “All systems—radar, control tower and flight operation systems—stopped working and this is very dangerous for a challenging airport like ours.”

Devendra KC, general manager at the airport, told the Post that there was a massive power fluctuation caused by the overuse of electricity at the airport. “The power back up system lasted for 25 minutes after electricity was disrupted. But we managed to use other systems to help planes land safely,” said KC.

Only two international airlines were placed on hold because of the power supply disruption, said KC.

Sichuan Airlines has been diverted to Lhasa, Nepal Airlines diverted to Delhi, Thai Airways to Kolkata, Salam Air to Patna, and Air China to Chengdu, according to the airport.

“We immediately ordered all units at the airport to switch off their ACs and other heating systems to stop the power fluctuation,” he told the Post. “Obviously, this is a serious issue. We have been encountering power fluctuation problems since last year.”

An emergency meeting has been called for later on Friday to resolve the problem.

According to an air traffic controller, the power system was down for 45 minutes—from 8:15 am to 9 am. It was interrupted again until 10 am.

“As all systems collapsed, there was no communication with airlines preparing to land or taking off,” said the air traffic controller.

After the power problem was resolved, the airport encountered yet another problem—the weather. The airport was closed from noon onwards as visibility reduced to 1,200 metres, according to KC.

A few international aircraft equipped with navigation performance approach procedures systems were allowed to land, as they only require 1,100 metres of visibility, said airport officials. For turboprop planes, 1,600 metres of visibility is required. However, international airlines using jet planes can take off at 800 metres visibility.

As visibility further worsened in the afternoon, international airlines equipped with the required navigation systems were also restricted to land, said KC.

Passengers have been warned that major delays and cancellations would continue, he said.

Anil Manandhar, media manager at Shree Airlines, said that except for a few flights to Nepalgunj and Dhangadhi early in the morning, all flights have been delayed, postponed or cancelled.

“Given the current weather pattern, we are not sure if flights will continue today,” said Manandhar.

The Meteorological Forecasting Division has predicted cloudy weather with moderate rain in some parts of the country. There are chances of light to moderate snowfall in many places and heavy snowfall in the high mountains. Rainfall is also likely to create thick fog across most parts of the country. This weather is expected to continue into Saturday. 

The story has been updated.