I believe your comments are based on a common misunderstanding of the physics of a sonic boom. The boom does not occur as the aircraft (or anything else) breaks the "sound barrier". It is in reality a pressure shock wave that is present whenever the aircraft is exceeding mach 1. The "crack" of a bullet is a miniature sonice boom! You can get mulitible booms from some aircraft because you get a separate shock cone from different parts of the aircarft. The F-18, and I've seen F-14 ones too, mpeg, if its the one I think it is, is actually demonstrating the low pressure areas surrounding various parts of the aircraft. WHat you are seeing is the moisture in the air condensing, due to decrease in pressure. I've seen those on aircraft on final approach, under the right conditions of temperature and humidity. I've even seen the same effect, or almost the same, sitting on the ground, but with the engines running. Some times you get a little mini tornado of water vapor going into the engine. When flying on a comercial aircraft you can sometimes see the effect when they put the spoilers up.