Former Jetstar chief executive Jayne Hrdlicka had been appointed the next head of The A2 Milk Company.
Ms Hrdlicka will remain with Qantas until March and join the dairy company at the start of the 2018/19 financial year, taking over from current A2 Milk CEO Geoffrey Babidge, who is retiring after seven years in the role.
The announcement comes less than a month after Ms Hrdlicka switched roles at Qantas to be head of its loyalty and digital ventures division.
Ms Hrdlicka joined the airline in 2010 as group executive of strategy and technology before she was appointed chief executive of Qantas' budget carrier Jetstar in 2012.
Qanatas chief executive Alan Joyce said Ms Hrdlicka had made a tremendous contribution to Qantas and Jetstar.
"Jayne has been instrumental in the expansion of Jetstar in Asia and she leaves with our best wishes for her next challenge," he said in a statement.
Qantas has yet to announce a replacement.
A2 Milk said Mr Babidge's retirement is part of a "carefully planned transition".
"Geoff has agreed to remain available to the company until the end of next year as an advisor to Jayne and the board as required to ensure a smooth handover and transition," the company said.
Ms Hrdlicka said she is delighted to be joining a "strong and principled" company.
"I look forward to working with Geoff to ensure we maintain his strong legacy through the transition," she said.
Her appointment follows the reorganisation of A2 Milk's senior team during 2017, including the appointment of Peter Nathan as chief executive of Asia Pacific.
A2 Milk chairman David Hearn said the company had conducted an "extensive global search" for a successor to Mr Babidge.
"The board is delighted to have attracted an executive of Jayne's calibre as CEO to continue the outstanding work which Geoff and his team have done over recent years," Mr Hearn said.
