PRIOR TO THIS FLT, THE PLT HAD CONTACTED A FSS & INQUIRED ABOUT THE WX. HE WAS ADVISED THAT VFR FLT TO TERRE HAUTE, IN, WAS NOT RECOMMENDED. HE TOOK OFF AT ABOUT 1830 CDT. THE PLT AGAIN CONTACTED THE FSS & INQUIRED ABOUT THE WX AT BURLINGTON, IA & SPRINGFIELD, IL (A PROBABLE ROUTE TO AVOID CONGESTED TRAFFIC IN THE CHICAGO, IL AREA). REPORTEDLY, THE WX IN THE BURLINGTON AREA WAS ACCEPTABLE, BUT THE PLT WAS AGAIN ADVISED THAT FLT TO TERRA HAUTE WAS NOT RECOMMENDED. THIS WAS THE LAST KNOWN RADIO CONTACT WITH THE ACFT. JUST PRIOR TO THE ACCIDENT, WITNESSES HEARD THE ACFT. ONE WITNESS HEARD THE ENG 'REV UP' & THEN SAW A BLINKING LIGHT, JUST BEFORE THE PLANE CRASHED. AN EXAM REVEALED THAT THE ACFT HAD SEPARATED IN FLT. THE R STABILIZER, LOWER HALF OF THE TAIL CONE, FORWARD SECTION OF THE VERTICAL STABILIZER, L FLAP & L WING WERE FOUND ABOUT 1 TO 1 1/2 MI FROM THE MAIN WRECKAGE. NO PRE-ACCIDENT PART FAILURE OR MALFUNCTION WAS FOUND. THE PLT HAD LOGGED 1 HR OF NIGHT TIME IN THE PRECEEDING 90 DAYS, BUT HAD NOT LOGGED NGT LNDGS DRG THAT TIME.