At about 1100 eastern time, a Beech V35B landed gear up at the Stennis International Airport after a local flight. The pilot stated that, while on a practice precision instrument landing, two airplanes flew over the runways thresh old at about 1,000 feet and two helicopters were hovering over the taxiway next to the runway. This activity distracted his attention and he did not lower the landing gear before landing. The airplane landed on its belly and skidded to a stop on the runway.