Australian airline Qantas is being prosecuted in a row over the duties of plane cleaners in early 2020.
A cleaner was told to stop working after he opposed cleaning practices on aircraft arriving from China.
Watchdog SafeWork NSW accused Qantas of discriminatory conduct for stopping the pay of a worker who raised concerns about exposure of employees to Covid.
However, Qantas said the cleaner was being investigated for "attempting to incite unprotected industrial action".
A union called the prosecution a "landmark for work health and safety".
Cleaner Theo Seremetidis was an elected health and safety representative at Qantas when the Covid pandemic broke out.
Last week, he told an Australian Senate inquiry that Qantas' safety precautions were inadequate: "We were directed to clean planes with just water. No sanitiser for the trays, no sanitiser for anything," he said.
"PPE was not mandated despite managers wearing HAZMAT suits. We were not even provided masks or disinfectant.
"These safety issues exposed workers in Australia, and more broadly, to serious risks of contracting and spreading Covid," he added.
"I was really passionate about safety, and wanted to see my fellow workers go home safely each day."
Mr Seremetidis alleges concerns raised with management went unaddressed and eventually he directed a group of workers to stop working.
"On the day that this occurred, I was stood down immediately. The day I was stood down was my last day at Qantas."
The workers safety regulator SafeWork NSW is prosecuting the airline, alleging the company engaged in discriminatory conduct.
"As the matter is before the court, no further information can be provided at this time," a SafeWork spokesman said.
Richard Olsen from the Transport Workers Union, which lodged the complaint, said: "The prosecution is the first of its kind anywhere in Australia.
"Qantas stood Theo down simply for trying to protect himself and his colleagues from Covid, and now the company is rightly facing criminal charges for doing so."
The airline said Mr Seremetidis did not follow the correct protocol for the industrial action he took: "There are established, legal mechanisms for health and safety representatives to follow if they have concerns.
"Qantas supports and encourages our employees to utilise these mechanisms if they have safety concerns.
"It's worth noting that there was not a single positive Covid case carried on our flights back from China."