There are no safe loopholes in a Covid-19 zero-tolerance policy. Evidence of this is to be found in hundreds of people being sent into quarantine at Penny’s Bay, a school closure and mass testing. This was after two Cathay Pacific cargo pilots, including one with a teacher-wife and two children at Discovery Bay International School, returned from Frankfurt testing positive for a strain of the Delta variant. The incident should prompt sympathy for everyone involved. But it also warrants some serious soul-searching. The pilots apparently mingled with a local community experiencing a fourth wave of contagion and rising case numbers. This has sparked calls for tightening or withdrawal of quarantine exemptions for aircrew. Cathay faces a dilemma amid the disruption of global supply chains by the pandemic. On the one hand, there are concerns that such a potential loophole could jeopardise the city’s efforts to match the mainland’s zero-tolerance policy in order to achieve a border reopening. On the other, Cathay warned that tightening measures would further disrupt the supply chain. A spokesman said: “It is important to maintain the flow of cargo between Hong Kong and the rest of the world.” The airline has mandated booster jabs for aircrew and requires all pilots and cabin crew who have stopped over in Frankfurt this month to quarantine for 21 days in a government facility. In addition, at the request of the Centre for Health Protection, the airline is stepping up checks on compliance with health and safety protocols at layover centres. The real issue is that the government has allowed airlines to regulate themselves. Every loophole has to be closed if Hong Kong is to remain free of local infections. The positive tests are reason enough to reassess whether quarantine exemptions for aircrew are still in the interests of public health. But perhaps Cathay needs to get its own act together. Cathay announces new self-isolation rules for aircrew returning to Hong Kong There is a need for more clarity about restrictions on pilots and aircrew in foreign locations. It is still not entirely clear whether they can go out and about or are confined to their rooms. That may be something that can be tightened up before reconsidering quarantine exemptions. There is, after all, a shortage of cargo pilots. The prospect of pilots seeing less of their families will not make it any better. That said, public health remains paramount.