Union member Ada So said about 400 cabin staff had gathered in front of the Cathay check-in desks.
She said more than 600 union members cast votes, with most in favor of taking job action.
They said they are protesting a cut to some cabin crew allowances, pay discrepancies for recently hired junior staff and a loss of legal support for workers involved in court cases such as civil action stemming from a passenger assault.
Cathay Pacific, Hong Kong's biggest airline, said it has no plans to change its "double-digit percentage" pay increase for staff promoted to permanent status after an initial 3-year term, and that crew meal allowances had an overall raise in the last half-yearly review. The carrier added that while some wording was dropped in a staff manual for handling unruly passengers, legal support remains unchanged.
The airport said in a statement that it was "taking measures to minimize the effects of the union's actions on airport operations.
