I flew on Singapore Airlines from London to Singapore last week.

Right after boarding, I noticed a passenger informing a stewardess that she was unwell and needed to lie down. The stewardess moved her to an empty row behind me.

The passenger was coughing and sniffling, and asked for blankets as she was feeling feverish and cold.

When I noticed that she had been sniffling and coughing continuously for a few minutes, I alerted a stewardess and asked her to provide the passenger with a face mask.

More importantly, I asked her to find out if the sick passenger should be flying on a full, long-haul flight in this condition.

No one attended to this matter and boarding continued. Finally, when I noticed that the plane started moving, I alerted another crew member, this time a steward.

The steward was nonchalant and said that nothing could be done because "she did not show symptoms before the hatch door was closed". This was untrue as the first crew member was alerted long before the plane took off.

The plane took off as we were speaking and the crew said they could not do anything else.

The sick passenger remained in the seat, visibly ill, coughing and sneezing in a cabin that was 90 per cent full, for the entire 13-hour flight.

I am shocked at the cavalier attitude with which the crew handled this matter. SIA must have protocol and policies in place to handle situations where one passenger poses a real contagion risk to everyone else on the plane.

Angela Xu Huifang