While on board a flight from Singapore to Jakarta, Ms Kanya noticed a fellow passenger taking items out of bags from different overhead compartments.
The Indonesian national, who wanted to be identified only by her first name, said she did not think this was unusual until the man, whose seat was across the aisle from hers, opened a third bag in a compartment farther down the aisle of the budget carrier. It was then that her suspicion was aroused.
Ms Kanya, 35, who has lived and worked in Singapore for about four years as a project manager at an international bank, said: "It was a flashy, funky-looking silver bag for youngsters. I didn't think the bag was his."
She had been on the way home to visit her family in Jakarta for Hari Raya celebrations, and said of the June 13 evening flight: "I fly this route quite often, and the airline is very strict on the number of items you can hand-carry. But this man seemed to have many bags, and I was wondering why."
When he started taking the items out of the bag one by one and studying them as if he was unfamiliar with the contents, Ms Kanya said, she realised those were not his belongings. "I've read somewhere about thefts that take place on overnight, long-haul flights. But this was a short-haul flight. The lights were on. The flight attendants were going back and forth selling refreshments. No one else seemed suspicious. I was a little unsure."
She said that although she saw the man taking all the items out and putting them back into the bag, she did not witness him stealing anything. She decided to report her observations to the flight attendant, who confirmed that a passenger seated at the back of the plane had reported earlier that his money had gone missing.
Just before the plane landed in Jakarta after the 11/2-hour flight, Ms Kanya said she saw another man walk over to the first man before passing him an object that she could not identify and whispering in a language she could not understand.
The flight crew alerted the authorities at Jakarta airport and the two men were apprehended after the plane landed.
The duo, who are Chinese nationals, had transited in Singapore while travelling from Hong Kong to Jakarta. They were sent back to Singapore on the same day.
Ms Kanya gave the police her statement shortly after she returned to Singapore the week after the incident.
The two men, aged 49 and 55, who had stolen cash amounting to $437, were each charged with five counts of theft with common intention and sentenced on Oct 11 to 19 months' jail.
Yesterday, Ms Kanya was commended for assisting the police and presented with the Public Spiritedness Award in a ceremony held at the Airport Police Division.
From January to September this year, there were a total of 13 cases of theft on board airplanes. There were 19 such cases in the same period last year.
Members of the public who are travelling overseas are advised to remain vigilant against crime and to take measures in securing their cash and valuables during their flights.