The aircraft was destroyed when it impacted the waters of Lake Harney, near Geneva, Florida. The airplane was registered to Planemarketing LLC, Vero Beach, Florida, and operated by L3 Airline Academy as CONN900 as a 14 Code of Federal Regulations Part 91 instructional flight. The Flight Instructor and two commercial pilots receiving instruction were fatally injured. Instrument and visual meteorological conditions prevailed in the area, and an instrument flight rules flight plan was filed for the flight, which originated from Sanford, Florida, about 0753. Review of preliminary information provided by the Federal Aviation Administration revealed that following an uneventful flight to Milledgeville, Georgia, the flight returned to the Orlando Sanford International Airport (SFB) and conducted a practice instrument approach to runway 09. After the flight completed the instrument approach, the active runway was changed to 27R and Air Traffic Control (ATC) controllers vectored the flight for a practice ILS Runway 27R instrument approach. About 2 minutes after the flight was given a vector to intercept the localizer and cleared for the approach, the controller issued a low altitude alert and advised the flight to climb to 1,600 feet. Following a second low altitude alert with instructions to immediately climb to 1,600 feet, the flight responded that "I am sir, I am." Shortly after, radar and radio communication with the accident airplane was lost. A witness, who was located on a boat near the north end of Lake Harney reported hearing a low flying airplane approach his position at a low altitude. The witness stated that he could not see the airplane initially due to low clouds and light ground fog, however, he observed the airplane below the cloud ceiling at 250 to 300 feet above ground level, and then climb rapidly. The witness further stated that they were looking in the general direction of the engine noise when they observed the airplane dive vertically into the lake south of their position.