Allowing air cargo crew to self-isolate after arriving in Hong Kong represents a major loophole in the city’s bid to keep out Covid-19’s new Omicron variant, medical experts have said, urging the government to change the policy. Calling the next two weeks crucial in determining if the variant had spread into the community, respiratory medicine expert Dr Leung Chi-chiu on Friday said authorities should tighten aircrew quarantine rules to further reduce any transmission risk.…