In Grand-Am, I believe, they run way different speed cars on the same track at the same time.

I think any time there is more then one model flying no matter the type there is a chance of a mid-air. They happen all the time with "regular" pattern models flying. I had a mid-air in the last round of qualifying at the Nats in 2010 and never saw it coming. Hit the only other Onas flying in the contest.