The flight crew noticed a bright red-orange spherical light flying parallel to their aircraft and reportedly maintained a constant distance and altitude, matching the aircraft's movements. The crew informed civilian air traffic control, which allegedly confirmed an unusual radar contact. Also military radar stations were reportedly alerted, and the object was also said to have appeared on military radar systems. 

Witnesses interviewed years later, including former radar operators and military personnel claimed that the object displayed extraordinary acceleration. 

According to later witness testimony, the Yugoslav Air Force scrambled MiG-21 interceptors to investigate but the UFO easily outmaneuvered the MiG-21 fighters, and one or more interceptors experienced serious problems, eventually a MiG-21 crashed and its pilot was killed after the encounter. However, this part of the story has never been independently verified through official military records and remains controversial.