We had this on an easyJet flight last summer. It started in the airport with very loud annoying repetitive tune on a game. I realised the child had ASD. His mother kept screaming at him to stop or use headphones to no avail. The rest of the large, extended family just ignored him.
As bad luck would have it, not only were they on our flight but sitting opposite, with the older siblings in front. The mother kept screaming at him to turn the sound down or wear earphones, to no avail. The flight was stuck on the tarmac, in the dark, for what seemed like hours- everyone at the back of the plane was getting desperate, my son (who it turned out was already freaking out as he had never been on a night flight before) was beside himself and, uncharacteristically said if they didn't take it off him he would do it for them, cue row of older siblings in front shouting that he was autistic and to leave him alone or he'd kick off, the mother kept screaming that she'd had enough and didn't know what to do with him, father sat there the entire time as if nothing was happening at all and it was nothing to do with him, earphones were found that didn't work, he refused to wear any anyway and refused to turn the sound down even a little bit.....it was pandemonium.
This is not intended to be SN-bashing, I work with a few SN children. However, the mother couldn't cope, the father was a waste of space and the siblings aggressive. Hopefully, next time they might find a way to be better prepared as it was very unfair to the rest of the passengers.