SINGAPORE - Singapore Airlines (SIA) has confirmed that 15 staff have tested positive for Covid-19 since March, with nine having fully recovered and been discharged.

According to an internal SIA company memo seen by The Straits Times and dated Thursday, April 23, the 15th case was of a "tech crew member" who last operated on the Auckland-Singapore route on March 29.

ST understands the term refers to pilots.

According to the memo, he reported the onset of symptoms on April 9 and was on medical leave until April 14. He was subsequently tested for Covid-19 as he continued to be unwell, and tested positive on April 17. He is currently warded in hospital.

"SIA has been providing all necessary support to our staff who test positive for Covid-19, and we continue to monitor the situation closely to take steps to ensure the health and safety of all customers and staff," the airline wrote in an e-mailed response to ST on Thursday.

Any unwell crew or pilot on board the flight will be attended to by the relevant medical authorities immediately after landing and will also be segregated from passengers upon displaying symptoms, SIA said.

As a precautionary measure, SIA said all crew members who operated on the same flights as the infected staff were grounded and asked to take a leave of absence.

The places that the infected staff could have visited have also been disinfected.

"We have worked with MOH (Ministry of Health) on all contact tracing activities when required," SIA said, adding that the ministry has confirmed that no SIA staff were infectious when they operated on flights.

Notably, the memo also says the infection number "does not include confirmed cases of Covid-19 in our overseas offices due (to) privacy and confidentiality laws in some countries".

In the same memo, SIA also said two vendors' staff have tested positive for Covid-19.

One works at Airline House and tested positive on April 19, while the other works at SIA's data centre and tested positive on April 22.

There are at least two cases at Airline House now, with an earlier case testing positive on April 5.

Other affected cabin crew - SIA's 12th, 13th and 14th cases - had operated on flights to places such as London and Amsterdam, according to earlier memos.

"As a precautionary measure, temporary adjustments have been made to our in-flight services on a number of flights. These include, but are not limited to, catering out of Singapore for all flight sectors, removal of seatback literature for selected cabins, as well as the temporary suspension of in-flight sales and hot towel service," the airline said.

Crew are provided with personal protective equipment such as masks and gloves, and all cabin crew have been wearing face masks since early March while serving aboard flights, SIA said.

SIA Engineering Company, which performs maintenance, repair and overhaul work on aircraft, has also reported several cases of Covid-19.

Two staff based at the airport apron area tested positive separately on April 11 and 15, earlier memos said.

The national carrier is beset by rapidly evaporating revenue, a common development around the world as the coronavirus pandemic pummels the aviation industry.

International air passenger traffic - which forms the majority of SIA's income - could nosedive by as many as 1.2 billion travellers by September 2020, said the International Civil Aviation Organisation (Icao) in its latest projections, with Europe and Asia-Pacific bearing the brunt.

To stem losses, SIA said more aircraft will begin carrying cargo instead of passengers, allowing its planes to carry up to 30 per cent more cargo.

The carrier has cancelled some 96 per cent of its scheduled passenger flights until the end of next month.