CNA Explains: Should you wear a mask on a plane if it's optional?

SINGAPORE: From Monday (Aug 29), Singapore will no longer require masks to be worn except on public transport and in healthcare settings. 

While masks are required on transport modes like the MRT and public buses, they are optional on private transport such as taxis and private bus services.

They are also not necessary at the airport, and may not even be required on flights. 

But should you still opt to wear a mask on a plane even if you don't have to? CNA asks some public health experts.

First off, which flights can you go on without a mask?

If the country you are travelling to or arriving from has a mask mandate, you'll have to wear one on the flight.

"Where there is a mandatory requirement for masks to be worn ... the mask must be worn on the flight itself," said the Health Ministry's director of medical services Kenneth Mak at a press conference on Wednesday. 

According to Singapore Airlines (SIA), some destinations which require passengers aged six and above to wear a mask on a flight are: Indonesia, Malaysia, South Korea, Cambodia, mainland China and Canada.

But many other destinations do not require masks on planes. These include Thailand, Taiwan, Japan, New Zealand, Maldives, the US and UK.

SIA said it will match its internal policy with the Singapore Government's. The airline will no longer require passengers to wear face masks from Aug 29, unless mandated by the place that the flight is travelling to or from.

Jetstar also said that it will ensure its mask policy "continues to be aligned with the relevant authorities" of the destinations it flies to.

How safe is flying without a mask? 

Although masks are optional on some flights, should you still wear one? Infectious diseases experts noted that ventilation standards for planes are high, and that there have been no major COVID-19 clusters originating from flights. 

“Travelling in commercial aircraft is much safer than people think,” said Professor Dale Fisher, senior consultant at the National University Hospital’s Division of Infectious Diseases. 

The air in a plane is changed over every three minutes, he said. About 60 per cent of the air entering the cabin is completely fresh and from outside, while the other 40 per cent is passed through hospital-grade HEPA, or high-efficiency particulate air filters, which remove 99.97 per cent of airborne particles. 

“This is why there have been no major clusters on planes. It is almost impossible for COVID particles to be wafting through a plane. So I think it is reasonable to not wear a mask – unless of course you have a respiratory infection,” said Prof Fisher. 

Travellers also remove their masks when eating and drinking on the plane, he noted. 

By not wearing a mask throughout the flight and taking them off sometimes, they would be exposing themselves to those around them during those periods, said Prof Fisher, who is also Professor of Medicine at the NUS Yong Loo Lin School of Medicine.

Another infectious diseases expert, Dr Leong Hoe Nam, said the HEPA filters are "as good as it gets".

But Dr Leong, who runs a private practice at Mount Elizabeth Novena Hospital, said transmission could still occur "three rows in front of and behind your seat".

“Given that passengers in coach are packed close together, this doesn't give much comfort. Business class and first-class patients will be exposed as well. All you need is one patient,” he told CNA. 

To avoid falling sick while on holiday, he advised travellers to continue wearing a mask on flights even if it is optional.

Who should wear a mask while on a flight?

Different individuals are at different levels of risk if they catch COVID-19, and this may influence their decision to wear a mask on a flight, experts said. 

For example, those who are younger or who have recovered recently from COVID-19 “may brave it”, said Dr Leong. 

However, some reports indicate that people could catch COVID-19 again as early as 17 days after a prior infection, he said. 

Those who are more vulnerable might choose to wear a mask if their immunity is poor, Dr Leong said. This could include transplant patients who are on various immunosuppressive drugs, cancer survivors, or if they are returning home to family members who are at higher risk. 

Professor Paul Tambyah, president of the Asia Pacific Society of Clinical Microbiology and Infection, advocated that travellers should do "whatever they are comfortable with".

“For people who are immunocompromised or who have not been infected before, it would probably be a good idea to wear a mask through the flight although this may be uncomfortable,” he added. 

“For those who are quadruple vaccinated and previously infected, the risks of severe disease are really low, so this is up to them.”

Prof Fisher agreed that vaccinated people are at very low risk of severe disease.

If someone seated nearby has symptoms, travellers could opt to wear a mask, he added. It would also be ideal if the cabin crew could ask passengers with symptoms to wear a mask. 

“As a matter of course, it would be reasonable to encourage mask wearing when you can't distance and you are very vulnerable. But that is not because they are on a plane,” said Prof Fisher, stressing again that the ventilation on commercial planes is superior “to almost any other setting”. 

What other precautions should you take?

Basic hygiene on the flight is important, said Prof Tambyah.

A study on H1N1 during a long-haul flight in 2009 also showed that sleeping through the flight was protective, he said.

“Personally, I think that climbing over someone to get to the toilet or the snack bar is a high-risk activity,” he added. "Having said that, not moving around on a plane puts one at risk of a deep vein thrombosis ('economy class syndrome') so we have to make some choices."

Dr Leong recommended that travellers wear a KN94, KN95 or N95 mask throughout their flights. 

They could also eat their meals before or after everyone else, and wipe down their chairs and tray tables with disposable, single-use alcohol wipes, he said. 

Many travellers also take their masks off in the toilet to breathe better, said Dr Leong. 

“But this may be their own undoing. The previous user could have left a ton of virus in the cubicle waiting for you.”