More than 500 engineers across major Australian airports began walking off the job from 3.30am on Friday and are set to strike until Saturday morning.
The airline is refusing to buckle to the union's demands for a 25 per cent pay rise over three years.
But the nationa's largest carrier said the strike action was having little effect on Christmas flights and as of 8.30am on Friday, 97 per cent of Qantas flights departed on time.
Qantas is is refusing to buckle to demands for a 25 per cent pay rise over three years. (Dave Hunt/AAP PHOTOS)
"We have put a number of contingencies in place and extra resourcing on the ground to ensure our customers get away as planned," a Qantas spokesperson said.
"As always at this time of year our aircraft are full and airports are busy, so we urge customers to give themselves more time to get through security and get to their aircraft."
Qantas said it was offering a competitive package including pay rises, upskilling and career progression.
The strike comes after a six-week pause in industrial action during which the parties resolved to continue negotiations over a new enterprise agreement.
The union consortium, made up of the Australian Manufacturing Workers' Union, Australian Workers' Union and Electrical Trades Union, said Qantas forced the walkout by refusing to negotiate.
Qantas is offering the workers a nine per cent pay rise over three years.
The latest strike by engineers comes after a six-week pause in industrial action. (Darren England/AAP PHOTOS)
Further industrial action is planned for next Friday and during the Christmas period.
"Workers were asked by Qantas in good faith to not take industrial action as a commitment to resolve bargaining," Australian Manufacturing Workers' Union secretary Steve Murphy said.
"For six weeks, Qantas has shown they cannot live up to their own values - they lied ... workers are feeling disrespected by the behaviour of Qantas and we all know how that feels."
Unions have been negotiating for a deal with the airline since April but were unable to reach agreement before the exisiting arrangements expired in June.
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