Unions are making a last-ditch plea to the consumer watchdog against a partnership between Qantas and Emirates airlines.
Tony Sheldon, national secretary of the Transport Workers' Union (TWU), along with other union representatives will front an Australian Consumer and Competition Commission (ACCC) conference on Friday.
Mr Sheldon says he will reiterate that the partnership is a bad deal on many fronts.
"It's bad for consumers, it's bad for the travelling public, it's bad for the economy and it's bad for the Australian workforce," he told reporters outside the conference in Sydney.
"Shrinking Qantas and handing over our national routes is putting our economic future into the hands of a Middle East carrier in a volatile part of the world."
Independent senator Nick Xenophon, who is also giving evidence, said the deal would mean further job losses.
"We will see a shrinking of the flying kangaroo and further job losses."
Earlier this month the ACCC gave Qantas and Emirates the green light to prepare joint strategies for sales, marketing and pricing.
But the ACCC has said its interim authorisation of the partnership may be reviewed at any time and should not be seen as an indication of whether final approval will be given or not.
Qantas said the unions were out of step by pushing an "anti-Emirates line" and the ACCC had indicated it would give the green light to the partnership because of the benefits for consumers.
"Three-quarters of Qantas staff support the partnership, as does the federal government, state tourism bodies, our shareholders and our customers," the airline said in a statement.
"We are pursuing this partnership as part of returning Qantas to international health."