Up to 400 security screeners at Sydney Airport are set to stage a three-hour stoppage on September 28, the Transport Workers' Union says, following two-hour walkouts earlier this week. The screeners work for Certis Security Australia and are pressing for higher pay and better job security.

The September 28 stoppage follows a separate 24-hour strike on September 24 by Qantas Ground Services, Australian airExpress and QantasLink workers at Sydney, Brisbane, Adelaide and Perth airports. Reuters reported that screeners joined that action with two sets of two-hour stoppages.

Union national secretary Michael Kaine called the action a last resort, saying workers have faced injuries and unsafe conditions. Sydney Airport has advised passengers to arrive early, monitor airline updates and allow extra time for screening on September 28.

Qantas said its contingency planning was designed to prevent major disruption and that mainline domestic and international services were not expected to be affected. The direct risk sits with regional and freight operations, according to the airline.

A further work-health-and-safety stoppage is listed from 10 pm on September 28 to 1 am on September 29, so travellers should keep checking airline advice.