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HONG KONG (Reuters) - Cathay Pacific Airways said it would guarantee thousands of first and business-class flights sold at huge discounts after a ticketing error, calling the mistake a surprise special on New Years Day.

The Hong Kong based carrier acknowledged the error on its twitter feed on Wednesday, stating “we made a mistake but we look forward to welcoming you on board with your ticket issued. Hope this will make your 2019 special too!”

The tickets are for flights from Vietnam to New York on Cathay Pacific for around $675 return instead of about $16,000 normally.

With the hashtags “Promisemadepromisekept” and “lessonlearnt” the carrier said it would maintain the economy fares.

The fares were not available on Cathay’s website on Thursday.

Online flight blogs and forums have been active with discussion on the deals since the error, with posts wagering on whether Cathay would honor the ticket fares.

Flyer Talk Evangelist wrote “Nobody here has noticed the hot mistake fare? ... Has been going on for hours. Wanna bet on the odd CX would honor this?”

The ticketing error caps a tough year for Cathay. The carrier has come under mounting criticism after it said in October that about 9.4 million passengers’ personal data had been accessed without authorization, seven months after it became aware of the breach.

The airline said it has spent over HK$1 billion ($127.7 million) on IT infrastructure and security over the past three years.