Air Serbia Flight 324

Investigation

Shortly after the accident, the Belgrade High Prosecutor's Office ordered police to determine the circumstances surrounding the collision. The Serbian Centre for Traffic Accident Investigation (Центар за истраживање несрећа у саобраћају — ЦИНС) also opened an investigation. According to the head of CINS, Nebojša Petrović, the investigation was complicated by the involvement of five other countries (Brazil, where the aircraft was manufactured, Denmark, where it was registered, Greece, where the operating airline was based and Italy and Poland, where the two pilots were from). The black boxes were sent to the US for analysis. The CINS released a preliminary report in the form of an Announcement of Investigation Commencement on 22 February 2024 which contained a timeline of events, classified the event as an accident and concludes that "one of the most probable causes of the accident was the inadequate assessment of the take-off parameters during the preflight preparation of the crew and after the decision to take-off with a shorter runway length compared to the initially planned one".

Despite statements from the head of the CINS from shortly after the accident that the investigation would be completed within three months, and a legal obligation to issue a report within a year, the agency issued an interim report in August 2025. It showed that the crew had not conducted a proper departure briefing and incorrectly calculated the required take off distance, and noted that the captain exerted pressure on the first officer to depart from the incorrect intersection. The investigation concluded that the cause of the accident was pilot error, the report, however, also criticised the airport procedures enacted after the aircraft landed, noting that the jet was initially parked at the terminal despite the major fuel leak, and only later towed to a remote stand.

In December 2025 CINS issued its final report, which reiterated that the accident was the result of a sequence of human error, issues with crew resource management and a systematical non-adherence to procedure. It noted issues with the operations manual of Marathon Airlines and made safety recommendations to the countries that issued the crews' pilot licenses, and remarked that the safety recommendation issued to Belgrade Airport pertaining to its emergency response plans was fulfilled.

According to aviation analyst Isa Alkalay, the air traffic controller on duty performed their job "by the book", as according to ICAO Annex 2 ("Rules of the Air") to the Chicago Convention, "The pilot-in-command of an aircraft shall have final authority as to the disposition of the aircraft while in command." Alkalay instead criticises the pilots' "incompetent" reaction and "the system" which allowed them to be certified, as well as the decision to park the aircraft leaking fuel by the terminal. The accident has been called the national airline's "most serious safety incident since the 90s".