On 23rd of August 2019, we took T9 Cardiff bus from Airport to City centre. The driver didn’t charge anyone any money.
I even asked to make a cash payment and he very graciously said Since I know you, you ride for free today.
Even though I know that was a joke, everybody did ride for free. Why would that be so? Even other passengers were wondering. One reason I could guess was the for some distance the road was under construction and was causing regular delays to the service.