Cathay Pacific on Friday said it is cancelling a small number of flights as some of its pilots are under the weather.

The flagship carrier said more pilots than expected have been absent this month due to seasonal illness, and so it has been cutting a small number of passenger flights, less than one percent of the total, since mid-December.

"Our operations remain normal overall, with a marked increase in the number of flights operated over the holiday peak season," it said in a statement.

Cathay apologised to customers affected by the cuts, and said it will do everything it can to minimise the disruption in this "exceptional" period.

A passenger surnamed Man who was supposed to fly to Beijing at noon on Friday said she spent two hours the night before trying to dial Cathay Pacific upon learning her flight was cancelled.

"My calls went unanswered...I got a bit anxious and didn't know what to do," she said. "I think it was very chaotic, because the airline's website was very slow, there wasn't a lot of information available, and I couldn't reach them by phone."

Another passenger, surnamed Lam, was given the option of rescheduling his flight to South Korea half an hour after he first learned about the cancellation.

"[Cathay] did pretty well by giving me an update in half an hour," he said, adding that the airline could have notified passengers two to three days in advance.

According to the Airport Authority's website, more than 20 Cathay passenger flights to and from Hong Kong were cancelled on Friday.