They apparently wanted to beat the queues for Apple's new iPhone, when the device became available in Singapore last Friday.
So the couple bought budget airline tickets to Malaysia - without any intention of using them - in order to enter Changi Airport's transit area to buy the iPhone 7 from a store there.
They got their phones, but the 26-year-old man and 25-year-old woman were later arrested by police for allegedly misusing their boarding passes to enter the transit area.
Revealing the case yesterday on its Facebook page, the Singapore Police Force said the pair had "no intention to depart Singapore", and investigations against the suspects are ongoing. Under the Protected Areas and Protected Places Act, offenders may be prosecuted in court and, if convicted, fined $1,000 or jailed for two years, or both.
While police did not identify the suspects, one is believed to be a Singaporean and the other, a permanent resident.
The Straits Times understands that after entering the transit area and buying their iPhones, the couple proceeded to the arrival and immigration hall. They apparently told airport staff that they wanted to remove themselves from another departing flight the airline had put them on, as they had missed the earlier one. They did not have any check-in luggage with them.
Airport staff then referred them to the authorities. They were subsequently questioned and arrested.
Since January, the police have arrested 15 people for misusing their boarding passes to enter the transit area at the airport.
Sources said these are often people who want to send off relatives or meet celebrities passing through Singapore.
"The transit areas of Changi Airport are gazetted as protected places," said the police on Facebook, adding that passengers who enter the transit hall with a boarding pass should be there only for the purpose of travelling.
Said security consultant T. Mogan: "Going into the transit hall to buy a phone may be seen as a mischievous act and we cannot tolerate such actions."
The managing director of Dragnet Private Investigation and Security Consultants added: "Considering the risks of terrorist acts, we cannot allow individuals to freely enter the transit area. If you buy a plane ticket, you should take your flight."
Passengers who check in for their flights but do not show up can cause a delay, said aviation experts.
Mr Greg Waldron, Asia managing editor of aviation information group Flightglobal, said: "There's a manifest of passengers on a flight that airline staff check against. Ultimately, the plane will have to get going but there will be a slight holdup.
"If there's a bag checked in, the airline will have to remove it from the plane, and this can cause a delay of 30 to 45 minutes."