French inquiry finds PC-12 and BN-2 crews unaware of each other before Caribbean airprox

French investigators have disclosed that a Pilatus PC-12 passed roughly 100ft directly above a Britten-Norman BN-2 while both were flying the same inter-island route in the Caribbean, with neither crew aware the other was there.

The two turboprops were operating commercial flights from Saint Martin to Saint Barthelemy on 28 December 2024, according to the BEA, France's accident investigation authority. The BN-2 departed Sint Maarten Princess Juliana airport's runway 10, followed about two minutes later by the PC-12.

The 17nm sector to Saint Barthelemy is flown at 1,500ft. The inquiry found the BN-2 was travelling at a groundspeed of 130kt while the PC-12, faster at 200kt, gradually closed the gap.

The BEA says Juliana tower passed no traffic information about the other flight even though both aircraft were on identical trajectories. The BN-2's transponder was not working, for reasons investigators could not establish, and the aircraft was not required to carry a collision-avoidance system, nor was one fitted.

As a result, the PC-12 pilot saw nothing on his collision-avoidance display, the inquiry says, which confirmed his belief that he was alone in the air. Although he was looking outside, the BEA found he was not actively searching for another aircraft.

Both aircraft contacted the aerodrome flight information service near the mandatory reporting waypoint GROUPER. The PC-12's radio communications were in French and the BN-2's in English, and each crew said it would call again at the next waypoint — a point known as PAIN DE SUCRE in one language and SUGARLOAF in the other. No traffic information was exchanged during the radio calls.

About two minutes later the PC-12 pilot disengaged.