[Mike Simonds]

I'm in favor of waiting until the kick is grounded and/or caught/recovered or is beyond the end line before blowing our whistles.

The reason being that the kick in flight can still be blocked and/or caught/recovered/touched.

Can you imagine what would happen if we blew our whistles and the defender who had a shot at blocking the kick suddenly stopped?

See my new thread on R blocking the kick in their end zone.