The pilot was taken into custody an hour before his flight was due to take off from London on Saturday night.
Police said weapons were discovered during a search of flight crew staff.
The pilot, reportedly 61, was taken to a local police station and has been bailed until next month.
There was no relief crew so passengers had to wait until Sunday to complete their journey.
A Scotland Yard spokesperson said, "Officers attended and subsequently a member of the flight crew, a man, was arrested on suspicion of possession of an offensive weapon in a public place and possession of a knife blade/sharp pointed article in a public place."
A Cathay Pacific spokesperson said, "Cathay Pacific can confirm that CX254 was delayed due to a crew-related incident concerning some items found in the pilot's hand luggage. At no point were passengers or staff put at risk."
"Given timings, Cathay Pacific were unable to organise a relief crew and therefore passengers experienced an overnight delay. Cathay Pacific takes this very seriously and is liaising with the relevant authorities," the spokesperson said.
