Qantas is appealing two rulings by the Federal Court, which found the outsourcing of baggage handlers, cleaners and ground staff was illegal.
Outside the court and before the hearing began in Canberra on Tuesday, Labor senator Tony Sheldon, a former TWU national secretary, said if the court ruled in favour of the airline "the immediate response will be to draft legislation".
"Quite clearly, this (Fair Work) legislation was put in by the Australian public through the Australian parliament and the Australian parliament will have the final say," he told reporters.
Qantas was found to have breached the Fair Work Act in outsourcing its ground operations to avoid enterprise bargaining rights, after the Transport Workers' Union brought legal action against the carrier.
Workplace Relations Minister Tony Burke is intervening in the case and has joined the union in responding to the appeal.
The airline argues it could not have breached the workplace rights of the employees, as they did not have the right to take protected industrial action at the time of the decision to outsource.
Justin Gleeson SC, for Qantas, told the court the airline's revenue stream had been "shattered" by the pandemic which left it "bleeding cash".
A Qantas spokesman said the airline's ability to legally outsource was to save more than $100 million a year when its survival wasn't guaranteed.
"When we made this decision we were still in the depth of the pandemic and there was very little certainty about when our recovery would begin," he said.
The spokesman said Qantas rejected the Federal Court's ruling that it was not convinced that preventing protected industrial action in 2021 was irrelevant in the decision to outsource.
TWU national secretary Michael Kaine said the court's ruling would impact all Australian workers' rights.
"The High Court will be asked to determine once and for all whether Qantas' outsourcing was not just cruel, irresponsible and bad for business, but whether it is confirmed as the largest case of illegal sackings in Australian history," he said.
Sacked Qantas worker Don Dixon said the airline decided to "make war" against its employees, which resulted in mental health issues, broken relationships, and financial loss.
"The plan was let's break these workers, well they haven't broken us," he said.
Maurice Blackburn principal lawyer Giri Sivaraman said Qantas lost the case on the facts.
"Now it's trying a legal argument to get the High Court to reduce protections in the Fair Work Act to make its actions lawful," he said.
"If Qantas wins, protections for all workers across Australia will be reduced."
The hearing continues, with judgment not expected to be handed down for some months.
