The low, fast war bird fly bys are exactly the reason I always keep an ARF on hand, I tell them once and then I fire up and fly low high speed passes just at the other side of the runway, this generally gets the point across if the verbal warning didn't. For some reason they don't like the Idea of flying their scale birds in the vicinity of a $100 Arf at high speed right down in front. As my father-in-law always tells m "there are some lessons that you can't learn from a book".Everyone in the hobby has done something stupid at some point and lost a plane or two, these young guys will learn too, as it becomes cost prohibitive to keep buying new planes and equipment.