What was found
VERY STRONG ELECTRIC BURNING ODOR IN COCKPIT AND AFT CABIN AREA AT CRUISE ALTITUDE. NO CAUSE IDENTIFIED. CHECKED CABIN AND LAV LIGHTING AND TRASH AREAS, NO DEFECTS. OPERATED BOTH PACKS USING APU AND ENGINES, RAN TRIM VALVES FULL HOT & COLD. OPERATED ENGINES AT FLEX POWER FOR 5 MINUTES, NO DEFECTS NOTED.