Mandala Airlines Flight 091 was a passenger flight operated by Mandala Airlines, which took off from Polonia International Airport in Medan, Indonesia, en route to Soekarno-Hatta International Airport in Jakarta. Shortly after takeoff, the aircraft, a Boeing 737-300, reported issues and lost altitude rapidly, crashing into a densely populated area near the airport. Reports suggest that the plane experienced engine failure attributed to mechanical problems. Eyewitnesses described seeing the aircraft struggling to gain height before it plummeted into homes, leading to a catastrophic situation both in the skies and on the ground.

The crash resulted in the deaths of all 149 individuals on board, comprising 138 passengers and 11 crew members. Additionally, several people on the ground were affected, and the crash destroyed multiple houses, increasing the impact of this tragic incident. Authorities launched investigations to determine the precise cause of the accident and to assess regulatory compliance by Mandala Airlines, focusing on maintenance practices and training protocols for the flight crew.

The disaster highlighted issues regarding aviation safety standards in Indonesia, where the regulatory environment and safety oversight had been under scrutiny. In the aftermath, the Indonesian government took measures to improve airline safety, leading to enhanced inspections and a push for airlines to adhere to international flying standards.