If you were stuck on a flight or bus with them?
A few years back DD (she's 10) developed a sniffing tic. We ignored it (with a lot of difficulty, it massively puts me on edge) and it went away. But it's back. And it's bad. At the moment she's sniffing every 5 seconds or so.
In a month we're going to a holiday flight then bus to destination. If you were stuck on a flight/bus with a 10 year old sniffing every 5 seconds how would you feel? In the car today and I almost wanted to get out and walk miles home rather than stay in the car.