Since the start of 2020 there have been 44 reported cases where COVID-19 transmission is thought to have been associated with a journey by air (including confirmed, probable and potential cases).

These statistics, published by Iata, seem to indicate the low incidence of inflight COVID-19 transmission.

“The risk of a passenger contracting COVID-19 while on board appears very low. With only 44 identified potential cases of flight-related transmission among 1.2 billion travellers, that’s one case for every 27 million travellers,” said Iata Medical Adviser, Dr David Powell.

He said the airline association recognised that this may be an underestimate but added that even if 90% of the cases were unreported, it would be one case for every 2.7 million travellers.

“We think these figures are extremely reassuring. Furthermore, the vast majority of published cases occurred before the wearing of face coverings inflight became widespread,” said Powell.

New insight into why the numbers are so low has come from the joint publication by Airbus, Boeing and Embraer of separate computational fluid dynamics research conducted by each manufacturer in their aircraft.

Powell said while methodologies differed slightly, each detailed simulation confirmed that aircraft airflow systems controlled the movement of particles in the cabin, limiting the spread of viruses. Data from the simulations yielded similar results: 
 

• Aircraft airflow systems, High Efficiency Particulate Air (HEPA) filters, the natural barrier of the seatback, the downward flow of air and high rates of air exchange, efficiently reduce the risk of disease transmission on board in normal times.
   
• The addition of mask-wearing amid pandemic concerns adds a further and significant extra layer of protection, which makes being seated in close proximity in an aircraft cabin safer than most other indoor environments.

Data collection

Iata’s data collection, and the results of the separate simulations, align with the low numbers reported in a recently published peer-reviewed study by Freedman and Wilder-Smith in the Journal of Travel Medicine.

Although there is no way to establish an exact tally of possible flight-associated cases, Iata’s outreach to airlines and public health authorities combined with a thorough review of available literature has not yielded any indication that on-board transmission is in any way common or widespread. Further, the Freedman/Wilder-Smith study points to the efficacy of mask-wearing in further reducing risk.
 

Layered approach of preventive measures

Mask-wearing on board was recommended by Iata in June and is a common requirement on most airlines since the subsequent publication and implementation of the Takeoff Guidance by ICAO.

This guidance adds multiple layers of protection on top of the airflow systems that already ensure a safe cabin environment with very low risks of inflight transmission of disease. 

“ICAO’s comprehensive guidance for safe air travel amid the COVID-19 crisis relies on multiple layers of protection, which involve the airports as well as the aircraft. Mask-wearing is one of the most visible,” said Powell.

“But managed queuing, contactless processing, reduced movement in the cabin, and simplified on-board services are among the multiple measures the aviation industry is taking to keep flying safe. And this is on top of the fact that airflow systems are designed to avoid the spread of disease with high airflow and air exchange rates, and highly effective filtration of any recycled air.”

He pointed out that aircraft design characteristics added a further layer of protection, contributing to the low incidence of inflight transmission. These include:
 

• Limited face-to-face interactions as passengers face forward and move about very little;
• The effect of the seatback acting as a physical barrier to air movement from one row to another;
• The minimisation of forward-aft flow of air, with a segmented flow design that is directed generally downward from ceiling to floor;
• The high rate of fresh air coming into the cabin. Air is exchanged 20-30 times per hour on board most aircraft, which compares very favourably with the average office space (average 2-3 times per hour) or schools (average 10-15 times per hour);
• The use of HEPA filters which have more than 99.9% bacteria/virus removal efficiency rate, ensuring that the air supply entering the cabin is not a pathway for introducing microbes.

Travellers feel safe

A recent Iata study found that 86% of recent travellers felt that the aviation industry’s COVID-19 measures were keeping them safe and were well implemented. 

“There is no single silver-bullet measure that will enable us to live and travel safely in the age of COVID-19. But the combination of measures that are being put in place is reassuring travellers the world over that COVID-19 has not defeated their freedom to fly. Nothing is completely risk-free,” said Alexandre de Juniac, Iata DG and CEO.

“But with just 44 published cases of potential inflight COVID-19 transmission among 1.2 billion travellers, the risk of contracting the virus on board appears to be in the same category as being struck by lightning.”