Straits Times political correspondent Linette Lai discussed a number of operational areas within the airport which could have been possible weak links that may have contributed to the formation of the Changi Airport Covid-19 cluster (What went wrong at Changi Airport?, May 22).

Do we not need to look further back along the likely chain of infection?

The guidance for travellers into Singapore published on the Immigration and Checkpoints Authority website, which reflects the latest travel policy as at last Wednesday, indicates that neither evidence of vaccination nor a negative polymerase chain reaction (PCR) test result is required for arriving Singapore citizens and permanent residents.

Surely, either proof of vaccination or a negative PCR test result not more than three days prior to departure should be regarded as the minimum requirement for any passenger boarding an aircraft bound for Singapore.

Brian Dalby