Opposition transport spokeswoman Bridget McKenzie is heading a committee on Australia's bilateral air services agreements that will begin hearings on Tuesday.
Senator McKenzie has been critical of Transport Minister Catherine King's decision to reject Qatar Airways' bid to double the 28 weekly services it currently offers in Australia, after being lobbied by Qantas.
Critics claim the move shields Qantas from competition and allows them to inflate airfares.
Though Ms King has claimed the decision was made in the national interest, she has not elaborated on the reasons.
This has led the opposition to accuse the government of having a cosy relationship with Qantas.
"I think it's unconscionable for the government to not come clean on the real reason for that decision," Senator McKenzie told Sky News on Monday.
"They are just looking shady and shifty as they don't produce documents, as they refuse to answer questions."
The committee is expecting to hear from the current and former heads of Qantas and other airlines, alongside representatives from airports and unions, economists, the Qatari ambassador, the consumer watchdog and the Productivity Commission.
Tuesday's hearings will focus on consumer concerns and issues at Sydney Airport after June report from the consumer watchdog alleged Qantas had cancelled flights to keep take-off and landing slots at the east coast airport.
Qatar Airways chief executive Akbar Al Baker was invited to the Tuesday hearing but declined, though he could appear at a later date.
Labor senator Tony Sheldon said he was "very disappointed" and that Mr Baker was no more above the law or parliamentary scrutiny than Qantas chairman Richard Goyder or its CEO Vanessa Hudson.
"Qatar Airways and the Qatar Civil Aviation Authority need to be hauled before this Committee in the coming days," he said in a statement.
However, Senator McKenzie remains confident all invited parties will assist the inquiry later on.
"In all our discussions thus far, they're very amenable to assisting the committee with their inquiries and I think that's a really positive thing."
The Australian carrier has faced a recent storm of PR disasters marked by a Senate grilling on its $2.47 billion profit during a cost-of-living crisis, a potential $250 million fine from the consumer watchdog for flight cancellations.
Compounding these issues are its former CEO Alan Joyce's expedited exit, and a major High Court loss which found the airline had illegally sacked 1600 workers during the COVID-19 pandemic.
The committee will hold four public hearings, one each in Sydney, Perth, Brisbane and Canberra.
Submissions for the inquiry closed on Monday and it is due to report by October 9.
