The move comes as part of ongoing work by the CMA in relation to holiday refunds during the coronavirus pandemic.

The investigation will consider situations where airlines continued to operate flights despite people being unable lawfully to travel for non-essential purposes in the UK or abroad, for example during the second lockdown in England in November.

The CMA is aware that, in some cases where flights were not cancelled, customers were not offered refunds even though they could not lawfully travel. Instead, many were offered the option to rebook or to receive a voucher.

The CMA recognises that the airlines sector, like many others, is under strain due to the pandemic. However, it is concerned that certain airlines may have breached consumers’ legal rights by failing to offer cash refunds, leaving people unfairly out of pocket, and has therefore opened an investigation to examine the matter further.

Andrea Coscelli, chief executive of the CMA, said: “We will be carefully analysing all the evidence to see whether any airlines breached consumers’ legal rights by refusing people cash refunds for flights they could not lawfully take.

“We recognise the continued pressure that businesses are currently facing, but they have a responsibility to treat consumers fairly and abide by their legal obligations.”