SINGAPORE — The Civil Aviation Authority of Singapore (CAAS) is tightening safety measures after two Singapore Airlines (SIA) crew tested positive for Covid-19 in the past four days.

With immediate effect, airline crew will be subjected to more frequent polymerase chain reaction (PCR) tests, CAAS said in a media release on Wednesday (Dec 30).

Those who layover in high risk destinations will be swabbed upon arrival and on the third and seventh day following their return to Singapore. Crew will be required to self-isolate until they receive a negative result from their seventh day PCR test.

Air crew on layover will also be required to further minimise their contact with locals. For example, food delivered through room service should be left outside the room at the door instead of being handed over.

In addition, crew travelling to and from South Africa will have to don full personal protective equipment, including N95 masks, face shields, protective gowns and gloves. Crew travelling to and from the United Kingdom are already doing this.

This is in addition to current measures, which require crew members to minimise interactions with passengers during flights, wear masks and use separate lavatories from passengers, among other things.

CAAS said all air crew undergo regular PCR tests upon returning from overseas. To date, more than 22,500 PCR tests have been carried out on air crew. All have tested negative, except for the two who tested positive on Dec 27 and Dec 29 respectively.

CAAS on Wednesday gave more details of the two cases.

The first is an SIA cabin crew who flew to New York on SQ24 on Dec 12 and returned to Singapore on SQ23 on Dec 16.

He was asymptomatic and was first tested on Dec 23, under a protocol that requires air crew to undergo a PCR test seven days after returning to Singapore. This test, as well as a second one on Dec 25, returned "inconclusive results", CAAS said.

However, an additional test on Dec 27 was positive.

The crew had been isolated at home since Dec 25.

All crew members and 16 passengers who were seated in the section of the aircraft cabin served by him on SQ23 have tested negative for Covid-19.

The second case is a pilot who last flew to London on SQ322 on Dec 19 and returned to Singapore on SQ317 on Dec 22.

He was tested on Dec 23, in accordance with a protocol for air crew who fly frequently, which returned negative.

The pilot then developed a fever on Dec 26 and went to a clinic the following day for another PCR test, which returned positive.

CAAS said its preliminary investigation showed that both crew had adhered to the mandated in-flight and layover measures, including wearing masks, minimising contact with passengers and locals, and staying in their hotel rooms.