The industrial action kicks off at Melbourne today and then on Monday.
Other airport strikes are planned around the country on 2 October and 4 October.
Engineers are seeking an initial 15% pay rise this year and the 5% annually.
The Qantas Engineers’ Alliance said the strike is ‘highly likely’ to impact flights.
Qantas says it has made contingency plans and doesn’t believe there will be widespread disruption.
However, the airline has offered passengers the option to change to earlier flights before the strike action begins.
The union says its members have gone without pay increases for nearly four years.
Steve Murphy, AMWU National Secretary, said: “Nothing has changed at Qantas —workers feel undervalued, underpaid and under-appreciated. If you’ve had a bad Qantas experience, well that’s nothing compared to how Qantas makes their workers feel every day.”