Qantas will face sentencing in a criminal court after a judge found the airline breached workplace health and safety law in the early days of the COVID-19 pandemic.

SafeWork NSW brought the rare prosecution after Qantas Ground Services stood down a trained health and safety representative hours after he gave a direction to others to cease work.

The February 2020 direction related to the cleaning and servicing of planes arriving from China and came the day after the federal government closed its borders to direct flights from that country.

Qantas later outlined several reasons in a letter as to why it suspended Theo Seremetidis from his job, but NSW District Court judge David Russell said that was an unsuccessful attempt to find additional reasons to back up its conduct.

“I have found that the reason for QGS engaging in discriminatory conduct towards Mr Seremetidis was because he exercised a power or performed a function as a health and safety representative,” he said in his judgment on Thursday.

The court dismissed other charges alleging the letter to Seremetidis constituted a threat and that his position was illegally altered.

Seremetidis was stood down and never worked for Qantas again. A year later, he was among more than 1700 workers illegally sacked by the airline.

The Transport Workers Union said it was a major victory for the worker.

“It holds great significance for all health and safety representatives, highlighting the crucial role they play in ensuring safe workplaces,” it said.

“The WHS Act has done its job.”

ACTU secretary Sally McManus also welcome the decision.

“As far as the union movement is concerned, Theo is a hero for standing up at great cost to himself to keep the whole of the community safe from a deadly virus at a time where no vaccines were available and when hospitals around the world were being overwhelmed,” she said.

“Qantas has shown us time and time again they will use every trick in the book to maximise their profits over the welfare of people.”

Both Safework NSW and Qantas can appeal the court’s decision.

-with AAP