What happened
On a flight from Charlotte Amalie Airport on Saint Thomas Island to San Juan, the de Havilland Heron operated by Prinair encountered fatal difficulties during its approach. At approximately 17:15 local time, the aircraft departed for an instrument flight rules (IFR) mission. By 17:32, the crew had established contact with San Juan Approach Control, reporting that they were maintaining an altitude of 4,000 feet.
During this communication, a trainee controller provided vectors for an ILS approach to runway 07. However, the instructions placed the aircraft at a position significantly different from its actual location; while the controller believed the plane was three miles east of Isla Verde, it was actually near the Fajardo intersection, roughly ten miles further east. Shortly after being cleared to descend to 3,000 feet, the aircraft struck trees in the Sierra de Luquillo mountains at an elevation of approximately 2,400 feet.
The wreckage was located about 24 km southeast of San Juan-Isla Verde Airport. The accident resulted in 18 fatalities, with no survivors among the occupants.
Findings
The investigation determined that the aircraft was vectored into high terrain while operating under IFR conditions without sufficient clearance from obstacles. This error occurred because the approach controller was performing tasks that exceeded his safe operational capabilities and lacked the necessary level of supervision.