The Airport Authority issued a notice to staff on Wednesday that said the restricted area will be segregated into a "green region" for mainland flights and an "orange region" for international flights from 5am on Monday.

The authority and contractors will arrange different teams to work in the two segregated areas. Each area will come with changing rooms, lounges and presentation halls to prevent staff from the two areas coming into contact.

The authority will set up a "CleanTech" disinfection facility in one of the corridors between the green and orange regions.

The notice said staff who handle international flights must pass through the passage and undergo disinfection before entering the area for mainland flights, but there is no similar restrictions for those from green to orange.

This came as health experts and even aviation unionists called for tightening or even cancellation of quarantine exemptions for aircrews, following the recent infections of two Cathay Pacific cargo flight pilots.

Speaking yesterday, the vice chairman of the Staffs and Workers Union of Hong Kong Civil Airlines, Li Wing-foo, said the arrangements for tightening aircrews' quarantine exemptions would depend on factors such as the airline's flight capacity and manpower.

Li said infections in aircrews had sparked public concern about a potential massive Covid-19 outbreak in the community.

University of Hong Kong microbiologist Ho Pak-leung urged authorities to scrap all aircrews' quarantine exemptions. Instead, aircrews would have to undergo quarantine in hotels before they are allowed to enter the community, he said.

But Cathay Pacific said tightening quarantine restrictions for cargo flight crews will greatly affect the company's operation of cargo flights, as it will burden the airline's manpower arrangement, adding that supply chains in Hong Kong may be seriously impacted.

The Centre for Health Protection said yesterday the two male Cathay pilots, 29 and 57, were infected by the highly infectious Delta Plus variant spreading in Europe.

Hong Kong yesterday saw three imported cases from the Philippines, Thailand and Saudi Arabia. All of them have been fully vaccinated but carried the L452R mutant strain likely to be the Delta variant.