Vietnam’s capital airport experienced one of the worst weather yet this year leading to numerous cancellations and diverted flights to nearby airports. On the 17th of February, Vietnam’s Noi Bai International Airport experienced its worst weather in 2022, up to 26 aircraft coming into the airport had to make diversions to nearby domestic airports as the foggy weather shows no signs of improving. Over 1000 passengers were affected as flights were either canceled or diverted, causing travelers to be sent to hotels if not strained in the terminal.

"VVNB 171530Z 06002KT 0800 R11R/1000N DZ FG VV002 19/19 Q1010 TEMPO 1200 DZ BR BKN002"

On Thursday night this week, Vietnam’s primary airport up North experienced its worst weather in the form of heavy fog and low clouds. Extensive heavy fog, also known as “cloud on ground”, was reported in Noi Bai International Airport, reducing runway visibility down to 800m with a cloud base of 200ft. According to the weather report from the airport issued at 2230 local time, the arrival runway 11R had horizontal visibility of 800m and more specifically with the horizontal visibility from the runway threshold of 1000m. However, the marginal visibility was not the main reason why aircraft had to divert. The reported cloud ceiling for the time was “BKN002” meaning over ¾ of the sky was covered in the cloud with the lower base of the cloud being 200ft above the airport. Low cloud at 200ft was the main reason for all the diversions and cancellations as it is below the operating minima for CAT I operations. The operating minima for the particular approach into Noi Bai Airport are 239ft, meaning that it would be illegal to land at the airport if the cloud base is less than 239ft if less than half the sky is covered. Despite the operating minima being only for CAT I operations and Noi Bai Airport being certified for CAT II operations, the airport removed the CAT II certification back in Sep 2021 possibly due to the renovation of the runways. With the CAT II certification, aircraft are able to continue to descent to 100ft until they have to make a decision to either continue or to execute a Go-around.

CAT I, CAT II, and CAT III

Instrument approaches are classified into 3 categories, with respect to the operating weather minima in case of weather with reduced visibility. In order for the aircraft to conduct CAT II and III approaches, qualifications will need to be obtained for various parties such as flight crew, airport (particular Instrument Landing System for the runway), aircraft capability, etc. These requirements have to go through a tedious and strict qualification process to fulfil the standard outlined by the ICAO for the airlines or airports to obtain the CAT II capability. CAT III capability, on the other hand, is just an addition to more harsh and strict requirements so the aircraft can land on the runway even without any visual references. For Noi Bai International Airport, the runways are currently certified for CAT I operations only. Therefore, even when some of the arriving airlines are certified for CAT II operation, they are forced to downgrade to CAT I operation as Noi Bai’s CAT I capability is the limiting factor.

Diversions to Laos, Hong Kong, and Domestic airports.

During the heavy fog, one international cargo flight diverted to Laos and one made an air return to Hong Kong. Up to 12 domestic flights were diverted to Haiphong(HPH), Danang(DAD), Thanh Hoa(THD), and Nha Trang(CXR). It was also reported that parking spaces were full in Danang Airport and some domestic flights diverted to smaller airports such as Thanh Hoa and Haiphong. One Japanese flight also diverted to Ho Chi Minh City’s Tan Son Nhat International airport.

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Passengers arriving at Danang International Airport after Hanoi Airport stop receiving flights.

Foggy Weather dissipated at 4 am

The heavy fog caused by rapid cold air moving from the South of China started to dissipate around 3 am with the airport starting to receive flights from around 4 a.m. Aircraft started to depart just before dawn, making a rare sight to see heavy traffic in the early morning.

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The heavy fog dissipated in the early morning. Noi Bai International Airport started receiving arrival flights again around 4 am in the morning.

Whilst it is not uncommon to experience foggy weather at this time of the year in the North of Vietnam, the disruption did bring additional financial burden for airlines and inconvenience for travellers. Airport facilities play an integral factor in the safety of low visibility operations and as the primary airport serving the country’s capital, it would be reassuring to see improvements in their handling of such weather when the CAT II capability is regained. With Vietnam reopening its border in March reopening its border in March, do you think the airport can handle all the traffic flow? Have you experienced any diversions as a passenger? let us know in the comments below.

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