A snap strike by Qantas staff over the national carrier's security practices caused major delays across Australia and grounded all international flights out of Sydney for up to four hours on Monday.
The Transport Workers Union accused Qantas of compromising safety and potentially risking a terrorist attack by failing to properly screen contractors before they begin work.
But the airline hit back, saying the union was trying to get political mileage out of the shooting of a Hells Angels bikie and the airport murder of his brother last week.
The union-led stop-work protests were held at the international and domestic terminals of Sydney, Perth, Adelaide and Brisbane airports from 9am local times on Monday, a union spokesman said.
Baggage handlers, caterers, cleaners and ground crew went on strike over plans by Qantas subsidiary Jetstar to outsource 100 baggage handling and check-in jobs at Sydney International, Hobart and Launceston airports.
Domestic passengers on flights arriving at Sydney airport were forced to leave without their luggage, while all flights at the city's international terminal were delayed by up to four hours.
Air New Zealand said one of its flights was cancelled and three flights were delayed due to the strike.
The union fears Qantas will put airport security at risk because the airline's new workers will only be given a temporary access pass to go airside under supervision, rather than undergo full clearance by the Australian Security Intelligence Organisation.
The union says all people need to do to get a temporary pass is to get a recommendation from an employer and show a driver's licence. The airline says all people working directly for Qantas, Jetstar or for a Qantas contractor undergo high-level security checks.
A union spokesman said Qantas managed to get domestic staff back to work by 11am, with an offer to dock them only two hours' pay. But international staff remained idle between 9am and 1pm (AEDT) after Qantas exercised its right to dock the maximum amount of pay for their industrial action.
The union said further strike action was possible.
