Qantas workers belonging to the Transport Workers Union will strike on Sept. 20 for four hours. The job walk-off is over enterprise negotiations, particularly a 5 per cent pay increase and clauses that would limit the use of contract labour.

The industrial action will begin at 7 a.m. on Tuesday in most eastern states airports, 3 p.m. in Canberra, 9 a.m. in Cairns and 5 a.m. in Western Australia.

About 3,800 baggage handlers, ground staff and other types of Qantas employees are expected to join the strike, which will also have running work bans to do higher duties or paperwork that could affect flights of the national flag carrier for two days.

The industrial action would be held mostly at the peak morning hours. It will happen at the same time that Qantas engineers will stop working for one hour at the Sydney Airport as part of separate rolling stoppages.

"The union is intentionally disrupting the travel plans of Australians. It is effectively holding passengers to ransom as it seeks pay rises, and attempting to place restrictions on Qantas, in essence, it is trying to run Qantas," Qantas group executive Olivia Wirth said in a statement.

She assured travelers that Qantas has contingency plans in place to minimise disruptions to ticket holders, and encouraged the TWU to continue negotiations with the air carrier rather than walk off their jobs.

"TWU members will take this industrial action as Qantas has left them with no choice," TWU lead negotiator Scott Connolly told AFP.

Mr Connolly said that TWU members have been patient and negotiated in good faith, but Qantas frustrated all the union's move to secure members' jobs and decent pay and work conditions. He said that while Qantas logged a yearly profit of $250 million which was double the 2010 profit and awarded Chief Executive Alan Joyce a 71 per cent salary increase to $5 million while stonewalling on the TWU enterprise negotiations.

Ms Wirth said the workers' demand are excessive and unreasonable, and accused TWU of conniving with the pilots' and aircraft engineers' unions to disrupt passenger travel.

The announcement of a strike came out amid reports of Qantas' plans to expand trips to China by launching next year five new carriers in a bid to get a larger cut of the Chinese passenger market.