Australia's Qantas Airways
Qantas said it expected more than 6,000 passengers to be affected during the day but many had been notified of the changes, avoiding scenes of chaos at Australian airports.
Flights were on average delayed by around 15 minutes and schedules were expected to return to normal in most major Australian cities by lunchtime, a Qantas spokesman told Reuters.
The Transport Workers Union, which represents baggage handlers and catering staff, said many airport staff had been locked out of the workplace since early Tuesday morning.
The strike was triggered by a dispute over pay and conditions and in opposition to planned domestic job cuts as the airline expands in Asia.
Qantas had not been notified of plans for further strikes at this stage, the airline spokesman said.
(Reporting by Michael Smith; Editing by Balazs Koranyi)