I've seen that same picture of the F/A18 Hornet. I think you can find it on wikepedia. The "vapor cone" is an amazing phenomenon that (to my knowledge) has NEVER been photographed THAT PERFECTLY in formation around a plane. It's an incredible thing when the air/humidity around the nosecone of the craft gets compressed to the point of BURSTING into a MASSIVE cone. And yep, it only happens near the speed of sound and the air density/humdity has to be JUST right for it to occur this beautifully.

I've seen some pretty fast planes (my friend's 109" P51D Scale will burn a low pass that's been clocked over 120mph) and last weekend I saw a competition 180"(?) Edge260 do a pass at well over 80mph and the throttle was barely 2/3 open (both were EXTREMELY IMPRESSIVE!!!!) > and BOTH were somewhere above "TOO DANG FAST!" for me flying

The fastest little bugger I've seen (granted I haven't looked for ULTRA-speed planes!) has been that Mig on the rcuniverse homepage that can pull fly-by's at 130mph!!!!! (however, launching with the "bungee" was one of the strangest things I've seen in a LONG time Granted, it's a very valid way to get a plane flying, it just looks WEIRD!)

Fast is Fast. But "Vapor Cone" pegs the speedometer at "Ludicrous"