Deputy Prime Minister Richard Marles says the government has "nothing to hide", as a cabinet colleague knocks back a Senate request to provide documents about its decision on Qatar Airways' flights.
A Senate select committee on commonwealth bilateral air service agreements is due to hold hearings next week, asking senior Qantas executives, as well as former CEO Alan Joyce, to appear.
The Senate has also requested the government to release documents relating to its decision to knock back Qatar Airways' application for a doubling of flights.
"There's nothing to hide," Mr Marles told Nine's Today show on Friday.
"A decision was made by the transport minister in the ordinary course of her work, as transport ministers have made over an extensive period of time, around how to apply the national interest in respect of this.
"And that's all that she's done."
Transport Minister Catherine King has claimed public interest immunity over documents relating to the Senate order.
She said in a letter that air services agreements were "treaty-level agreements between countries".
"There is a public interest in not disclosing such discussions so the government's negotiations over air services agreements with a range of countries can continue unimpeded."
Nationals senator Bridget McKenzie, who is chairing the committee, said the government was continuing its cover-up.
"It is shocking that Transport Minister Catherine King waited until parliament rose to tell us that she will now not be disclosing advice from her department on why she blocked more Qatar Airways flights based on 'public interest immunity'," Senator McKenzie said.
"After giving nine different excuses for her decision, it will be up to the Senate inquiry to try to get to the bottom of this fiasco."
Greens leader Adam Bandt called the minister's move disappointing.
"The public deserves to know what advice the government got about the decision that was made," he said.
The Senate inquiry will also look at federal government decisions on additional air services going back to 2016.
Mr Bandt said if the government was serious about taking action, it would consider bringing Qantas back into public ownership and treating it as an essential service.
Senator McKenzie has flagged Qantas's unlawful outsourcing decisions during the COVID-19 pandemic could also be examined.
She has accused the Albanese government of having a "cozy, personal and political relationship" with Qantas.
Senator McKenzie admitted the former coalition government had partially knocked back Qatar Airways in the past but said the committee would look at previous decisions to help open up the aviation market.
Asked whether former transport minister Michael McCormack should front the inquiry, she said: "The department that worked for the former minister will be called and we'll be asked those questions."
Past transport ministers she had spoken with said Qantas had been "very muscular" in its advocacy to government.
"They all agreed that the culture of Qantas was very aggressive about protecting their market share," Senator McKenzie said.
The inquiry will examine whether a lack of competition in the aviation sector is pushing up airfare prices and impacting the tourism and hospitality sectors.
It is due to report by October 9.