Qantas Airways Limited (ASX: QAN) will face off against employees in the High Court of Australia on Wednesday.
Four unions are appealing against a Full Federal Court decision last month that the airline did not have to provide sick, compassionate or carer's leave for staff that had been stood down.
Qantas stood down about 20,000 employees at the start of the COVID-19 pandemic when it became apparent its planes would be grounded.
The Australian Council of Trade Unions (ACTU) claims Qantas' denial forced some seriously ill workers to take a redundancy for financial reasons.
"Qantas' behaviour toward the most unwell people in its workforce has been callous and illegal," said ACTU assistant secretary Scott Connolly.
"Stand downs are meant to be strictly limited to particular circumstances, but even in those circumstances workers should not be prevented from taking leave or being paid their basic entitlements."
Connolly added the High Court result could have ramifications for all Australian businesses and workers.
"This appeal is not just important for Qantas employees who've been unfairly denied access to their own sick, compassionate, personal or carer's leave, it's critical to all workers in Australia who may be stood down in the future."
The airline did provide annual and long service leave during the coronavirus stand down.
The Motley Fool has contacted Qantas for comment.
Running battle with its own staff
Law firm Maurice Blackburn is handling the appeal on behalf of the Transport Workers Union (TWU), the Electrical Trades Union (ETU), the Australian Workers Union (AWU) and Australian Manufacturing Workers Union (AMWU).
"Denying sick workers the leave they have built up and pushing them in some cases out of their jobs in order to access redundancy payments to pay bills is utterly despicable," said TWU national secretary Michael Kaine.
"Qantas has received over $800 million in taxpayers' support to help it during the pandemic but instead of acting like a responsible employer in return it is trashing lives and trashing jobs."
There was one dissenting judge, Justice Mordy Bromberg, in the Full Federal Court hearing. The unions are pursuing his line of argument in the High Court.
"The corollary of this contention is that there is no entitlement to any kind of paid leave whatsoever, whenever an employee cannot be usefully employed," he said in the judgment.
"That notion is startling in its reach and effect."
Just last week Qantas had a separate court victory against the unions. The Full Federal Court reversed an earlier judgment that the airline had illegally pocketed JobKeeper payments that should have been passed along to employees.
