Korean Air Cargo Flight 8509 was a Boeing 747-2B5F, registered HL7451 bound for Milan Malpensa Airport, that crashed due to instrument malfunction and pilot error on 22 December 1999 shortly after take-off from London Stansted Airport where the final leg of its route from South Korea to Italy had begun.

The aircraft crashed into Hatfield Forest near the village of Great Hallingbury, close to, but clear of, some houses, killing all four crew members on board.

[7] Following the plane's departure from Tashkent on the previous flight segment, one of its inertial navigation units (INUs) had partially failed, providing erroneous roll data to the captain's attitude director indicator (ADI or artificial horizon).

[7] The first officer, whose own ADI displayed the correct angle of bank, according to information from the aircraft's flight data recorder,[1] failed to participate in full crew resource management techniques, saying nothing to challenge his captain's actions nor making any attempt to take over the flight with his own controls.

[7] Data from the flight recorder indicate that during this time the control wheel was commanding the aircraft into a steeper left bank.

[7] The first recommendation of the AAIB's final accident report was that: Korean Air continue to update their training and Flight Quality Assurance programmes, to accommodate Crew Resource Management evolution and industry developments, to address issues specific to their operational environment and ensure adaptation of imported training material to accommodate the Korean culture.