Qantas and its chief executive Alan Joyce have received a letter from SafeWork NSW saying it is investigating the airline's suspension of an aircraft cleaner in early February who raised concerns about workers being exposed to coronavirus.

Key points: A worker was stood down from Qantas in early February after telling employees it was not safe to work on aircraft arriving from China

A worker was stood down from Qantas in early February after telling employees it was not safe to work on aircraft arriving from China Qantas said the worker was telling employees information that was against advice of health authorities

Qantas said the worker was telling employees information that was against advice of health authorities A Qantas spokesman said the company had received a letter from SafeWork NSW and is working with the regulator

The employee, who is a union delegate and elected health and safety representative, was stood down on February 2 pending an investigation for raising concerns about coronavirus exposure at work at Sydney Airport.

Qantas has refused to reinstate the worker.

A Qantas spokesman said the airline would work with SafeWork NSW on its investigation.

"A union delegate was stood down pending an investigation after incorrectly telling employees it was not safe to work on aircraft arriving from China in early February," he said.

"This was against the advice of health authorities and despite additional safety equipment being provided to employees."

Transport Workers' Union (TWU) NSW branch secretary Richard Olsen said Qantas could face the first prosecution of its kind in Australia, with the airline possibly facing multiple breaches for "discriminatory conduct and prohibited behaviour" against the worker.

Each breach carries a fine of $500,000, he said.

"If safety reps at Qantas can't stand up to unsafe work practices, then no worker is safe," Mr Olsen said.

"The TWU believes there is ample evidence to prove that Qantas engaged in discriminatory and prohibited behaviour.

"It is incomprehensible to the TWU that the Sydney worker was stood down due to his concerns for his co-workers."

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TWU wants details on how Qantas will protect workers

Qantas temporarily stood down 20,000 of its 30,000 workers on March 18 in response to the coronavirus crisis.

"Now with the company-wide stand down, Qantas have put their own internal investigation on hold, leaving the worker uncertain of his future, and we are watching the company scramble to manage their own actions," Mr Olsen said.

"Qantas's behaviour from the start of this pandemic has been outrageous."

Eleven Qantas baggage handlers at Adelaide Airport tested positive to coronavirus this week, and more than 100 baggage handlers and ground staff are self-isolating for 14 days.

Mr Olsen said the TWU had written to Qantas demanding information and documents under workplace health and safety laws about procedures in place to protect workers.

The union also wrote to Adelaide Airport about workers from various companies who have been potentially exposed.

"With Qantas baggage handlers in another state now infected, there have clearly been fundamental problems in how Qantas has managed this across its network," he said.

"We demand that the worker Qantas stood down in Sydney is reinstated and we demand that the airline steps up and begins acting responsibly.

"This must be done to protect workers but also the travelling public."

A Qantas spokesman said since the coronavirus outbreak, the company had put "enhanced safety measures in place to protect our employees and customers".

"We are conducting additional cleaning of airport facilities and aircraft on a daily basis," he said.

In a separate matter, SafeWork NSW issued Improvement Notices on Qantas in March, after the regulator observed that cleaners were required to board Qantas planes to handle wet and used tissues, used face masks and soiled nappies.

The regulator had said at the time that cleaners and passengers were exposed to the risk of being infected with COVID-19.