FAILURE OF THE PILOT-IN-COMMAND OF N2409K TO MAINTAIN SAFE SEPARATION FROM N2437K DURING UNAUTHORIZED FORMATION MANEUVERING. OVERCONFIDENCE IN PERSONAL ABILITY AND THE EXECUTIVE OF UNAUTHORIZED FORMATION FLIGHT ON THE PART OF BOTH PILOTS-IN-COMMAND WERE FACTORS IN THE ACCIDENT. THE LACK OF TOTAL EXPERIENCE OF BOTH PILOTS-IN-COMMAND WAS ALSO A FACTOR IN THE ACCIDENT.