On May 7, 1997, at 1100 eastern daylight time, a Learjet 31A, N31PV, sustained structural damage while maneuvering over the Atlantic Ocean. The airplane was operated by Federal Investment under the provisions of Title 14 CFR Part 91 and visual flight rules. Although the prevailing weather was visual meteorological conditions, an instrument flight plan had been filed for this training flight. The airline transport pilot in command and his commercial pilot first officer were not injured, nor was the one passenger. The airplane sustained substantial damage. The flight originated in Fort Lauderdale, Florida at 1015. The Learjet was on a training flight which departed Fort Lauderdale-Hollywood International Airport, flew over Orlando, and returned to Fort Lauderdale Executive Airport. While over the Atlantic Ocean at 23,000 feet, the airplane received a clearance to descend to 13,000 feet. The instructor pilot took control of the airplane to demonstrate an emergency descent. While descending, the first officer believed the instructor pilot to be disoriented and assisted with the recovery. The instructor pilot commented that they were "up to red line", and he was "disoriented by the vibration". He stated that he believed the vibration to be from a previous encounter with hail. They recovered the airplane before 13,000 feet was reached. Upon landing at Fort Lauderdale Executive, it was noted that the single point refueling door, aft of the right wing, was missing and that there was substantial damage to the horizontal stabilizer. Both of this parts were replaced, and the airplane was restored to flight status. This airplane was a new aircraft with only 34 hours of total aircraft flight time. Prior to this accident, the airplane had been inspected one other time. This inspection followed a flight in which the airplane was showered with hail after flying near a thunderstorm. This inspection noted hail damage to the engine and nose cone. Both the engine nacelle and the nose cone were subsequently replaced, and the aircraft was cleared for flight. No other damage was noted.