Staff at Sydney Airport's domestic and international terminals will undertake a second four-hour stoppage on Friday evening, after walking off the job in the morning.
The workers, contracted by the airport from security firm Certis Group, are demanding more full time jobs, fairer rostering and no cuts to hours.
Transport Workers Union National Secretary Michael Kaine said the decision to strike came after unsuccessful bargaining talks with the company on Thursday.
He said the company had pressed forward with plans to cut minimum hours by six hours per week.
"Sydney Airport has squeezed Certis so hard that it wants to turn these jobs into scraps of gig work with no stability," he said.
"They will strike again this evening to fight for their job security and to rebuild what used to be good, secure jobs at our airports."
The industrial action comes following months of enterprise agreement negotiations between Certis, its staff and the union.
The union claims job insecurity and limited pay have left some critical security staff fatigued and forced to work multiple jobs.
"This is not just about the security and safety of these workers," Mr Kaine said.
"It's about the security and safety of all passengers flying in our airways, and we've got to make sure that we get that recipe right."
Certis Group, meanwhile, claimed it remained committed to negotiating in good faith and had put a fresh offer to staff as recently as Thursday.
"We are disappointed that, with that offer on the table, the TWU has chosen instead to proceed with industrial action that affects the travelling public," a spokesperson told AAP.
The union has also demanded Sydney Airport, which is not party to the negotiations, step in to improve pay and conditions.
A spokesperson for Sydney Airport said it was working with its partners to minimise disruption and maintain passenger safety.
"We recommend passengers travelling today allow extra time and stay alert for messages from their airline," they told AAP.
The negotiations spilled over into a series of separate walk-offs from the airport in late September, involving a reported 400 staff.
Security staff, including those working in passenger and operational screening functions, are expected to strike from 6am to 10am and 5pm to 9pm.
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