A business class return ticket to NY from Vietnam's Da Nang costs around $16,000 for travel in July and September, according Cathay's website on Wednesday.
Earlier in the week, the Hong Kong airline sold business class return tickets normally listed as costing US$16,000 (NT$492,000) between Da Nang in Vietnam and NY in July and September from a mere US$675 (NT$20,700), Bloomberg reported.
It was not clear how many tickets had been sold and Cathay Pacific did not immediately respond to requests from the BBC. "Cathay Pacific will be honoring all of these first and business class mistake fares", the blog continued. Prices weren't available for August.
Despite the costly error, the airline says it will honour the tickets sold at the discounted price. On Wednesday, the same journey cost around $16,000 for July and September, according to the airline's website.
"Happy 2019 all, and to those who bought our good - VERY good surprise "special" on New Year's Day, yes - we made a mistake but we look forward to welcoming you on board with your ticket issued", the company said.
"Hope this will make your 2019 "special" too!"
Flights from Hanoi to Vancouver and back in a mix of business and first-class seats could cost less than $1,000, according to a post on One Mile at a Time.
When Cathay Pacific noticed the gaffe, it was forced to admit its pricing mistake.
Twitter users who said they had bought the cheap tickets lined up to welcome the news, though at least one questioned whether it was a publicity stunt - something an airline representative denied.
The pricing gaffe comes just months after a sophisticated hack on Cathay Pacific's computer systems a year ago that exposed private information of 9.4 million passengers. In 2014, Singapore Airlines made the same mistake and honored those fares as well.
Last year, British Airways sold tickets on routes to Dubai and Tel Aviv for as little as £167.
And even though the carrier could cancel the tickets, it announced that the fares would still stand.