Several more Qantas flights, both international and domestic, have been crewed by staff with Covid-19, raising new questions about the safety of the exemption from the 14-day self isolation rule for airline crews.

The new revelations come as the Transport Workers Union says it lodged notice alleging a breach of workplace safety against Qantas on Wednesday, after another of its members – a freight worker – was diagnosed with the virus in Sydney.

Qantas strongly rejects the union’s claims and says the worker acquired coronavirus from a family member.

There has already been a cluster of eight cases among baggage handlers in Adelaide, which is being investigated.

The TWU told Qantas it believed the airline had failed to reduce the risk of infection to workers, “resulting in infection of a significant number of workers in its operations in Sydney and interstate, and the likely exposure of hundreds more”.

The union is demanding information on the number of workers who have been infected with Covid-19, the steps taken to isolate workers who may have been in contact with the virus and copies of hazard management plans to minimise the risk of infection.

In the case of the freight worker, Qantas said the TWU’s claims were baseless and accused the union of trying to gain political mileage from the misfortune of its members.

“The union knows full well that this employee most likely contracted Covid-19 from a family member who already had the virus, and not while they were at work, a spokesman said.

Qantas insists that transmission of coronavirus to its workers on flights is low risk, despite social distancing being difficult or impossible on planes.

Both the federal government and Qantas are keen to resume scheduled flights to help stranded Australians later this week.

But all states are now publishing lists of flights where there have been incidences of Covid-19 as part of their efforts to track and trace exposure within the community.

The advice on the New South Wales Health website for passengers on flights with a confirmed case of Covid-19 is that they must self-isolate for 14 days.

This already applies to passengers from overseas who are now being held in hotels but the advice is extended to those seated near an infected passenger on a domestic flight.

But this does not apply to crew on affected flights.

Some listings on the state health websites include a warning for a few rows. But more recent entries are for entire planes, which suggests that it was the cabin crew who are infected.

For example, new data posted on the NSW Health website shows that a flight to Darwin from Sydney on 1 April and Darwin/Sydney flight operated on 2 April, a Sydney/Darwin flight on 3 April and a Darwin/Sydney flight on 4 April had a Covid-positive person on board. The notification is for all rows, which strongly suggests it was a cabin crew member who was infected.

Another flight between Sydney and Maroochydore and back again on 26 March has also been notified for all rows.

The Guardian has also learned that four crew members have tested positive following a flight from Dallas to Sydney, QF8, which landed on 27 March. The crew are understood to have socialised in Dallas.

Qantas has not confirmed the infections of the Dallas crew but the flight is now listed on the NSW Health site and all passengers are being notified.

Comment has been sought from Qantas.

Another cluster among crew who operated a rescue flight from Lima on 29 March has been confirmed by Qantas.

Qantas’s chief medical officer, Ian Hosegood, said: “The government’s exemption for air crew from mandatory self-isolation is critical to allow repatriations flights to happen and help stranded Australians get home safely.

“We have introduced enhanced measures to further protect our crew while they are overseas. Pilots and cabin crew will be required to self-isolate in their hotel rooms and we are putting in place other measures in-flight,” he said.

Qantas said the staff on the Lima flight were believed to have got it in Santiago.

The 14-day isolation rule applies to all international passengers. The government is now insisting that they be housed in hotels for their period of quarantine. But a number of states have also introduced quarantine rules for their residents returning from other states.

Yet cabin crew remain exempt, despite growing cases of them getting Covid-19 while overseas. As of last Friday, Qantas said that 50 of its employees had contracted coronavirus.

The TWU NSW branch secretary, Richard Olsen, said Qantas had failed to protect its workforce.

“Workers at Sydney airport and at airports around the country are scared and they are not getting the support from Qantas.

“With confirmation of yet another worker infected, people right across the airline will be worried about going home to their families and spreading the infection to them,” he said.

“We believe that Qantas is in breach of workplace health and safety laws and has not been putting in place systems to minimise the risk.”

The union said one crew member had been sent an email on 6 April asking whether they recalled interacting with a passenger in a particular seat on a flight three weeks earlier – on 19 March, the day the Ruby Princess passengers disembarked.

In a statement to the Guardian, Qantas said earlier in the week: “There’s been no confirmed cases of transmission of the coronavirus to employees or customers on board our aircraft, or any aircraft globally for that matter. Whilst this transmission is possible, current evidence suggests it’s unlikely.”

Qantas has said that as community transmission increases across the globe it will adapt its protocols on board and for operating crew to protect staff and customers.

The airline said it had introduced enhanced measures to further protect crew while they are overseas.

“In most of these cases, the employees have contracted the coronavirus while overseas, including staff who were on holidays,” Hosegood said last week.