Without details of the hypothetical scenario made here, we cannot know if that’s the case. If the ticket purchaser was unable to see the circus because their flight home was delayed, the circus has no obligation to refund them. If attendance of “Circus 2” is offered to the purchaser due to the cancellation of “Circus 1” under the conditions of the original ticket purchase, then it’s unlikely to be an unfair contact.
There are all kinds of details missing here that we can freely speculate about.