Qantas Airways says about 150 of its employees and 250 contractors will go as part of changes to its engineering operations.
The job losses were due to overstaffing of line maintenance positions at Qantas' Sydney base, and as work on cabin interiors of some aircraft was completed, the airline said on Thursday.
There would also be cuts to staff numbers at Qantas Defence Services - which maintains the Australian Defence Force's C130 Hercules aircraft - and a consolidation of engineering training facilities from Melbourne to an existing facility in Sydney, the airline said.
The details of the job losses are in line with the airline's previous announcements of job cuts in its maintenance divisions.
Qantas also said it was adding up to 120 positions at its Brisbane maintenance facility as work was transferred from the airline's Tullamarine site in Melbourne, which has closed.
The airline had already added 100 positions in Brisbane since May.
"The changes will result in a net reduction of around 150 Qantas employees and 250 contractors from a workforce of around 30,000 across Australia," Qantas said in a statement on Thursday.
Line maintenance is usually carried out on aircraft daily, either in between flights or overnight, and includes minor repairs or modifications and visual inspections.
Qantas domestic chief executive Lyell Strambi said newer aircraft arriving into the fleet required less maintenance than the older aircraft they were replacing.
Affected staff would be offered assistance to relocate to Brisbane, or redeployment to other roles at the company, he said.
"I believe we have some of the most highly skilled and capable engineers in the world," Mr Strambi said in a statement.
"Unfortunately we just have too many for the work we have right now and the work we expect to have in future.
"Knowing how long it takes to build engineering skill and capability we have avoided making these decisions for as long as we could."
The airline closed down its Tullamarine facility in August, and planned to eventually consolidate all its heavy maintenance work for Boeing 737, 767 and Airbus A330 aircraft on one site.
Australian Licenced Aircraft Engineers Association federal secretary Steve Purvinas said the job cuts threatened safety.
"In our view, the current levels of understaffing are becoming dangerous and Qantas management are disregarding basic laws of aviation safety," Mr Purvinas said in a statement.
"This needs to stop or Qantas risks becoming an unsafe operator."
Australian Workers' Union Victorian secretary Cesar Melhem urged Qantas to make every effort to redeploy those who have lost their jobs at Avalon.
"These are highly-skilled aviation mechanical engineers who have worked to help build the Qantas reputation for safety," Mr Melhem said in a statement.
"It is unthinkable that they are cast aside in this way."
At 1358 AEDT, Qantas was down 1.75 cents, or 1.35 per cent, at $1.28.