Last summer, Hong Kong Airlines suffered a similar error, and set the bar high by honouring its mistake. It sold business class tickets for HK$4600 ($875) for return flights from Los Angeles to both Shanghai and Bangkok. The airline was widely praised after it admitted to the error but said it would cover all bookings. As of Tuesday, the same tickets were selling for HK$30,000.
New York-based Chris Dong, who writes about airlines on the Point Me To The Plane website, was getting ready for his new year celebration when he got wind of the cheap Cathay fares. He got a first class ticket from Da Nang in Vietnam to John F Kennedy airport in New York for HK$6600.
"While they are becoming less common, I've seen a handful of business class and economy fare deals before," he said.
"First class deals are way less common - many airlines simply don't have a first class and if they do, their pricing is heavily guarded so the odds of a 'deal' coming around are really rare."
He predicted Cathay would demonstrate goodwill by honouring all of the tickets sold, going by the apologetic approach it took in its recent data breach which hit 9.4 million customers.
JT Genter, who writes about airlines and reviews flights for travel website The Points Guy, described the cheap fares as "a great way for passengers to get to experience such an excellent product for themselves".
Genter and his wife Katie spent US$2365 ($3500) each for three round-trip flights in first and business class.
"I'm thrilled to now be able to share the highly regarded first class product with my wife on this trip," he said.
It is unclear how many first and business class tickets were sold.
Carriers such as Cathay typically generate bigger profits from premium tickets and it has been in this section of the plane where the loss-making airline's business has seen a stronger recovery in bookings compared with economy class, where it is still experiencing a glut in competition, according to the airline.
By lunchtime on Tuesday, when a Post reporter tried to buy a first class return ticket to Boston from Da Nang via Hong Kong for HK$9800 ($1860), the airline's website was producing an error, stating it was suffering from "technical difficulties".
Pricing errors could be covered under contract law in Hong Kong, leaving the sale of the tickets voidable at the behest of the seller. In the United States, the Department of Transportation says airlines can cancel fares if an error is proven.
Cathay appeared to be monitoring the issue on social media.
Twitter user Mac Frost said he booked two first class trips on Cathay in February and September. "My new year's resolution is to spend as much of 2019 as possible eating caviar and napping in the sky."
When he posted his tweet around noon, the airline "liked" his message soon after, to which Mac Frost responded: "If you cancel the fare after liking this tweet I will cry."
- South China Morning Post