During these altitude fluctuations, the controller twice provided instructions to the pilot to contact the Memphis Air Route Traffic Control Center; however, neither of the instructions were acknowledged by the pilot. During the final moments of the flight, a faint communication from the pilot stating the airplane’s registration and “Debonaire” followed by an emergency declaration and an unintelligible word. About 60 seconds later, a faint and largely unintelligible transmission from the passenger was transmitted.
Aviation Investigation Preliminary Report - N5891J