Keeping the middle seats of an aeroplane empty helps to reduce coronavirus transmission onboard, research suggests.
Restrictions are easing across the UK, however, it is still illegal to travel abroad for holidays.
From 21 June, officials in England hope to "be in a position to remove all legal limits on social contact".
International travel hinges on the number of coronavirus cases and immunisation success overseas, as well as the complex issue of whether to introduce so-called vaccine passports.
With many concerned travelling will trigger further coronavirus waves, not to mention the introduction of new variants, scientists from the US Centers for Disease Control and Prevention (CDC) analysed how the risk could be mitigated.
A laboratory model suggests keeping the middle seats vacant on a single or twin-aisle aircraft reduces the passengers' coronavirus exposure by up to 57%.
Aeroplanes can hold "large numbers of persons in close proximity for long periods", raising the risk of coronavirus transmission if an infected passenger or cabin crew member is onboard.
With the extent of this risk being unclear, the CDC scientists used aerosol-emitting mannequins to measure the flow of virus particles through mock-up aircrafts.
They did not account for the wearing of face coverings, which are enforced on flights in England and Scotland amid the pandemic.
The effects of vaccination were also not considered. Non-essential travel is not permitted in the UK even among those who have had a jab.
The UK's three vaccines – Pfizer-BioNTech, University of Oxford-AstraZeneca and Moderna – were approved after demonstrating they ward off severe disease with the coronavirus, not the infection itself.
Research increasingly suggests, however, the jabs help to stem transmission.
Watch: Travel restrictions to be eased in Scotland from 16 April
The results of the CDC study suggest a passenger in the same row but "two seats away" from a coronavirus patient is 23% less likely to catch the infection than if they were in the "adjacent middle seat".
When extrapolating this exposure to a full 120-passenger cabin, this risk reduction ranges from 35% to 39%, the results show.
Read more: Travelling boosts happiness
Keeping the middle seat vacant "in a scenario involving a three-row section that contained a mix of coronavirus sources and other passengers" was found to reduce the exposure risk by 57%.
An aeroplane's ventilation system is "designed to deliver amounts of clean air per occupant that conform to various standards", wrote the CDC scientists.
"When these standards are adhered to, most virus particles are removed within several seat rows from a source on an aircraft".
This same ventilation can also "cause some turbulent dispersion", however.
The CDC scientists pointed out wearing a face covering would further help to stem transmission, as well as preventing coronavirus contamination on surfaces.
Face coverings themselves do not eliminate the risk, however, with the team recommending "multicomponent prevention strategies as good practices".
Watch: Do coronavirus vaccines affect fertility?