Aer Lingus has said it will review its procedures following a claim it did not maintain social distancing among passengers on a Belfast-London flight.
But when can air passengers expect things to return to the way they were before coronavirus?
How many people are still flying?
Far fewer people are flying since the Foreign Office advised against international travel.
Between 16 and 22 April, for example, the number of air passengers coming into the UK was 99% lower than the same period in 2019.
American Airlines said social distancing had been possible "for all passengers", suggesting that its aircraft have a lot of empty seats.
And Virgin Atlantic said many of its flights in April were only a quarter full.
Meanwhile, Ryanair carried 40,000 passengers in April - down from 13.5 million in the same month last year.
With the holiday trade almost completely dried up, most of those flying were UK nationals returning home.
How safe is air travel?
If you have to fly, it's a common belief that you are more likely to become ill on an aeroplane, because you're breathing "stale" air.
However, according to the World Health Organization, the quality of air in a plane cabin is very carefully controlled and changed up to 30 times an hour.
However, there is a greater likelihood of the virus being transmitted if passengers are close together - usually as a result of an infected individual coughing, sneezing or touching surfaces.
This is the same as in any other situation in which people are close to each other, such as on a train or a bus.
Most seats were occupied on the Belfast-Heathrow flight, despite government guidance people should stay two metres apart. Sean Mallan
What's the advice for air travellers?
Public Health England says passengers should sit as far apart as possible.
The National Travel Health Network and Centre - which was set up by the Department of Health - offers the following advice:
- Avoid moving from your seat unnecessarily, but exercise your legs (flex and extend the ankles) to encourage blood flow
- Only use the designated toilet for your area and wash your hands before leaving
- If you start to feel unwell, stay in your seat and speak to the air crew
You should not be travelling if you are unwell, or if you have tested positive for Covid-19.
At UK airports, the advice is similar to that given in any large public building - keep your distance from others, and use the hand sanitisers provided by the airport. Shops and restaurants have been mostly closed and people are discouraged from entering the terminal unless they are travelling.
Can there be social distancing on flights?
EasyJet has said it plans to keep the middle seats on planes empty once the lockdown is lifted.
The airline suggested the measure could be taken for a short period as flying resumed. Emirates and the US airline Delta have announced similar plans.
But not all airlines are happy about the prospect.
Michael O'Leary, the boss of Ryanair, has said empty seats do not ensure safe social distancing and are financially unviable.
The International Air Transport Association (IATA), the body representing global airlines, says leaving the middle seat empty would not improve passenger safety. It says most airlines would not have made money last year if a third of the seats had been removed.
The chief executive of Heathrow Airport, John Holland-Kaye, raised concerns about getting passengers on and off flights. "It's just physically impossible to socially distance with any volume of passengers in an airport," he said.
Many airports have taken measures to help enforce social distancing rules. Getty Images
What about other measures?
Mr Holland-Kaye has called for a common international standard for health screening at airports "to build confidence in international travel". He has also pushed back against Public Health England's verdict that temperature checks for passengers are ineffective, asking for the evidence to be published.
He also suggested people passing through airports should wear face masks, "as people from Asia have been doing ever since Sars (virus) came out".
UK ministers have suggested that they might consider a 14-day quarantine for anyone arriving in the country.
Home Secretary Priti Patel told the Home Affairs Select Committee that while the government's decisions were informed by scientific advice, "everything is under review".
But Airlines UK, which represents British Airways, easyJet, Virgin Atlantic and Ryanair, are opposed to the measure, calling it a "blunt tool measure".