The Covid-19 coronavirus is still relatively new, so accurate data on how it can spread between aircraft passengers is in short supply. But previous studies have looked at
the spread of other respiratory illnesses. Based on the available information, US Centers for Disease Control and Prevention generally tries to track down people sitting in the two rows in front and the two rows behind passengers found to have serious infections.
A 2018 study by researchers from Emory University in Atlanta attempted to model how passengers and crew moved about an aircraft, and how that might affect the transmission of infectious diseases. "A droplet-mediated respiratory infectious disease is unlikely to be directly transmitted beyond one metre from the infectious passenger. Thus, transmission is limited to one row in front of or in back of an infectious passenger," the researchers concluded.
But contrary to this,
earlier research - led by the same academics - had shown that in real life cases passengers with Sars or influenza actually appeared to have infected a number of people well outside their immediate area. Their explanation was that some of those who became ill had become infected in the airport, while embarking or disembarking from the plane, or from touching contaminated surfaces, rather than by breathing in infected droplets.
"Filtration only works on mass airflows, most of the transmission during a plane journey will be those short-range face-to-face conversations. Close range aerosol transmission is what you have to be worried about on a plane, train or a bus - this is the biggest risk."
And even if you are further away, the risk is not eliminated, says Dr Tang. "How long Covid-19 can remain airborne depends on a range of factors. It varies between different people, it varies depending on the state of your infection, and you can't say all the droplets will fall to the ground within two metres. Some smaller droplets can stay suspended and travel up to 16 metres - and they all could be carrying the virus."
BBC - Coronavirus: How safe is it to get on a plane?