The Caravan departed Itaituba (ITB) at 06:40 on a flight to Jacareacanga (JCR). Jacareacanga Radio was contacted five minutes later. The crew were informed that visibility was poor: ceiling at 0 feet with a visibility of 300 meters, which was below minimums. The Caravan circled the airport to wait for the weather to improve. At 07:37 Jacareacanga Radio tried to contact the flight, but no answer was received. It appeared that the airplane had flown into the ground. Investigation revealed that the pilot was underqualified. The flight was being operated as an air taxi flight, which meant that it had to be piloted by an ATPL pilot. The pilot however just had a PPL and did not have an IFR rating. CONCLUSION: Operational Factor: (1). Adverse Weather Conditions – Contributed Weather conditions were unfavorable at the destination location for visual flight. There was a layer of fog near the forest. (2). Poor Instruction – Contributed The Commander was not qualified to fly that type of aircraft and was not instrument cleared. (3). Disabled Judge – Contributed The pilots continued the flight, even knowing the adverse weather conditions at their destination. (4). Flight Indiscipline – Contributed One of the pilots was not qualified to fly that aircraft and, in addition, there was intentional disobedience to the air traffic rules and regulations, regarding the non observance of the minimum IFR flight level in the industry. (5) Disabled Oversight – Contributed There was poor oversight of the responsible company by letting an unqualified pilot operate the aircraft. (6) Weak Cabin Coordination – Contributed IFR flight without complying with IMA 100-12 rules, conducted below the limits and outside the descent profile are indications that there was no planning/coordination in the operations performed in the cockpit.