In countries where restaurants, malls and other venues are open to the public, there is a standard requirement of social distancing of at least one metre, if not two. So why is this not enforced on planes?
Emirates, like most airlines operating today, does not enforce social distancing as a rule, but this week it announced that passengers could purchase spare seats.
Adel Al Redha, chief operating officer at Emirates said the airline realised that some customers wanted to guarantee a gap between them and their neighbour.
"We have not implemented [keeping] middle seats [free] as some of the airlines have announced. Where possible, we space people at the time of check-in to give more space between passengers," he told Dubai Eye's Business Breakfast radio show.
Now passengers can pay for peace of mind and buy up to three adjoining seats at the check-in desk, for Dh200 to Dh600 each, plus taxes.
While passengers might want to stay apart on planes, the International Air Transport Association (Iata), which represents 290 airlines or 82 per cent of total air traffic, said there is no requirement for social distancing measures.
The association quoted aviation authorities such as the US Federal Aviation Administration, the EU Aviation Safety Agency and the International Civil Aviation Organisation (ICAO), a UN agency that works to ensure safety in international air transport.
The World Health Organisation refers to the ICAO for its recommendations on air travel.
The imperative for social distancing rests on how transmissible Covid-19 is on an aircraft. The ICAO said distancing was not necessary, as long as passengers wore masks at all times during flights. This is the most effective way of curbing the spread of Covid-19.
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"When needed, seats should be assigned for adequate physical distancing between passengers. Airlines should allow for separated seating arrangements when occupancy allows it," the ICAO said.
For its part, the WHO said international travel should always be prioritised for emergencies and aid work, though it emphasised that "international travellers should not be considered by nature as suspected Covid-19 cases or contacts".
In its latest travel advice, Iata said its research showed travellers did not catch Covid-19 on planes.
“There have been millions of flights since the start of the Covid-19 outbreak resulting in a few confirmed cases of transmission in-flight," the trade body said on its website.
“Unlike other modes of transport, the aircraft cabin environment makes the transmission of viruses difficult, and we have seen a low occurrence of onboard transmission."
Iata said that from January until October last year, there were 44 confirmed or possible cases of Covid-19 associated with onboard spreading, out of the 1.2 billion passengers that travelled during the same period.
It is known that many thousands of passengers have flown with Covid-19, including over the winter holidays, but did not necessarily spread the virus on the flight.
Air filter quality crucial
Aside from the wearing of masks, air quality is the main reason for the low number of infections onboard aircraft.
Planes have high-efficiency particulate air filters, which remove 99.9 per cent of bacteria and viruses, and are similar to those found in hospital operating theatres or industrial clean rooms. The air is also exchanged 20 to 30 times every hour onboard most aircraft.
“The cabin air quality, with the use of these filters, called Hepa, wheedle out every microbe and virus,” said John Strickland, director of aviation consultancy JLS Consulting.
"While there cannot be any guarantees, the systems combined with compulsory mask-wearing mean that confidence can be high that it is the best possible environment.
“The air, contrary to people's impression, is changed with incredible regularity – every few minutes.
"On top of that, the way the air circles in the plane, it's a downward flow so it's not carrying stuff up towards you.
"It has certainly got me convinced. I haven't flown for a year, but I feel more confident about getting on a flight than I do about going to a local restaurant."
While passengers are sitting in close proximity on an aircraft, the forward orientation of passengers and seat backs also limit transmission from row-to-row, Iata said.
"No environment is risk-free, but few environments are as controlled as the aircraft cabin. And we need to make sure that travellers understand that," said Iata chief executive Alexandre de Juniac.
Iata said passengers should wear a mask at all times, over their nose and mouth, and change it when it becomes damp, by which stage it is no longer functional.
While not a deciding factor, there is also a financial consideration, said Saj Ahmad, chief analyst of StrategicAero Research.
"On longer, intercontinental flights, it's simply impossible for an airline to break even, let alone be profitable if seats are blocked out," Mr Ahmad said.
"For Emirates, they’d be losing upward of 150 or more seats on some of its densely configured A380s."