Tui has launched an investigation into claims mask-wearing was not enforced on a flight after some passengers tested positive for Covid-19.

All passengers on flight 6215 from Zante to Cardiff in Wales on August 25 have been told to self-isolate for a fortnight.

Tui has now contacted all 193 passengers and crew on board at the request of Public Health Wales after 16 people from different groups on board tested positive for the virus.

The company said it would investigate claims by passenger Stephanie Whitfield after she told the BBC many of those on the flight were talking and not wearing masks.

It said: “The health and safety of passengers is always our priority and we are concerned to hear of Mrs Whitfield’s claims.

“Our crew are trained to the highest standards and in line with European Union Aviation Safety Agency (EASA) guidelines.

“Passengers are informed prior to travel and via PA announcements on the flight that they have to wear masks throughout and are not allowed to move around the cabin.

“Masks can only be removed when consuming food and drink. A full investigation is now underway as these concerns weren’t reported during the flight or before today. “

Tui said all its aircraft were deep cleaned after every flight and fully disinfected at least once every 24 hours and equipped with state-of-the-art, hospital standard HEPA air filtering system.

Unite, the union for aviation workers in the UK, said in a statement: “The UK government and the civil aviation authorities must promote and enforce a clear policy on the wearing of face coverings and masks for airline passengers. It should not simply be left to ground staff and cabin crew to police the public during this pandemic.

“Passengers must be totally clear on this policy, their responsibilities and the penalties if they fail to abide by the rules before they even arrive at the airport.”

It added: “Passengers have to be given clear direction.  They should be informed that travel through an airport and on an aircraft will requires the wearing of a mask or face covering, unless there are clear medical exemptions for the individual passenger.

“Passengers should be informed of such a policy, and that refusal to abide by this policy will incur denied boarding, removal from a flight, or a financial penalty and even a travel ban.

“We would also urge the industry and the UK government to make it a priority to get a common approach agreed across all common travel areas.”