Press Release – Science Media Centre Research contracted by the aviation sector models the effect of selectively relaxing our border restrictions depending on each countrys Covid-19 risk level. It is a model of how we could manage international arrivals by their country of origin, … Research contracted by the aviation sector models the effect of selectively relaxing our border restrictions depending on each country’s Covid-19 risk level. It is a model of how we could manage international arrivals by their country of origin, and suggests we could offer quarantine-free travel or shorter stays in quarantine to arrivals from some less Covid-afflicted areas.