I couldn't tell you if it's a state or Federal regulation, but we did have to inform local airports when a team and I put up a small weather balloon, and that was just a few pounds. If you're planning on flying a 5 foot aluminum rocket, you will be way over that. I have to agree, the safety considerations here are a little... thin. I might suggest you look at a company called Public Missiles Ltd: they sell high power rocketry parts (airframes, fins, recovery devices, etc) made out of phenolic tubing (cardboard) and G10 fiberglass. This is a safer, lighter, and cheaper alternative to aluminum. Also: If you plan on flying this and you don't have a certification from either NAR or Tripoli, I suggest you begin looking into that before you decide to fly. I fly at Tripoli-sponsored launches and it works out fine. If you decide to fly on your own, you may have legal issues, issues which you can avoid by flying with experienced hobbyists. So, look into a local NAR/Tripoli chapter, get your certifications, and then go ahead and fly. Good luck!