Fourteen people boarded a small turboprop on the morning of January 10, 1995, at Sultan Muhammad Salahudin Airport on the island of Sumbawa. Their destination was Ruteng, a mountain town on the island of Flores, a short hop across the waters of eastern Indonesia. The aircraft -- a de Havilland Canada DHC-6 Twin Otter 300, registered as PK-NUK and named Sangihe -- never arrived. Somewhere over the Molo Strait, the narrow body of water between Sumbawa and Flores, the plane and everyone aboard simply vanished. No wreckage was recovered. No bodies were found. No emergency transmission was received. Merpati Nusantara Airlines Flight 6715 became one of the enduring mysteries of Indonesian aviation, a disappearance made all the more haunting by the modest scale of the flight and the completeness of the silence that followed.
The Twin Otter was built for exactly this kind of flying. Manufactured by de Havilland Canada in 1973, the DHC-6-300 was a rugged, twin-engine workhorse designed for short runways, remote airstrips, and the demanding conditions of island-hopping aviation. Powered by two Pratt & Whitney Canada PT6A-27 turboprops, the type had earned a reputation for reliability across decades of service in some of the world's most challenging environments -- Arctic tundra, jungle clearings, mountain valleys. Merpati Nusantara Airlines, Indonesia's domestic carrier specializing in remote regional routes, operated a fleet of Twin Otters to connect the scattered islands of the archipelago. The flight from Sumbawa to Ruteng was routine, a short crossing over water that pilots on the route had made hundreds of times. Four crew members and ten passengers were aboard.
The Molo Strait separates Sumbawa from the western coast of Flores, a stretch of water where weather can change with little warning. Conditions on January 10, 1995, were poor. The region's equatorial climate produces intense convective storms, and the strait's geography -- warm water between volcanic islands -- creates localized weather patterns that can overwhelm small aircraft. After departure from Sultan Muhammad Salahudin Airport, Flight 6715 headed east toward Frans Sales Lega Airport in Ruteng. At some point during the crossing, contact was lost. There was no distress call, no position report indicating trouble. The aircraft simply stopped communicating. Search efforts focused on the waters of the Molo Strait and the coastline of western Flores, but the sea yielded nothing. In these waters, depths can exceed several hundred meters, and currents are strong. Whatever happened to PK-NUK, the strait kept it.
Investigators offered two primary hypotheses. The first and most widely cited pointed to weather. Severe conditions at the time of the flight could have produced downdrafts, turbulence, or icing capable of overwhelming even a proven airframe like the Twin Otter. A sudden loss of control in instrument conditions over water, at low altitude, would leave almost no time for a distress call. The second theory was more troubling: an explosion in the cargo hold. Whether from improperly declared cargo, a mechanical failure, or sabotage, an in-flight detonation would explain the complete absence of a debris field if the aircraft broke apart at altitude and scattered across a wide area of deep water. Neither theory was ever confirmed. Without physical evidence -- no flight data recorder, no cockpit voice recorder, no wreckage of any kind -- the investigation could reach no definitive conclusion. Flight 6715 joined a small and somber list of aircraft that have simply disappeared.
What makes a disappearance different from a crash is the absence of closure. A crash site, however devastating, provides evidence, explanation, and a place to grieve. The families of the four crew members and ten passengers aboard Flight 6715 received none of these. The aircraft was never found. The cause was never determined. In the years that followed, Indonesia would experience other aviation tragedies that drew far greater international attention -- the loss of AirAsia Flight 8501 in 2014, Lion Air Flight 610 in 2018. But Flight 6715 belongs to an earlier and quieter category of loss: small planes on remote routes, serving communities that depend on aviation because geography offers no alternative. The Twin Otter connected islands that roads could not reach and ferries served infrequently. For the people of Sumbawa and Flores, these flights were not luxuries. They were lifelines.
The Molo Strait flows on, indifferent to the aircraft that lies somewhere in its depths. Fishing boats cross the same waters daily. Ferries carry passengers between the same islands. The route that Flight 6715 flew is still flown, though Merpati Nusantara Airlines itself ceased operations in 2014 after years of financial difficulty and safety concerns. The Twin Otter type remains in service worldwide, still valued for its ability to operate where other aircraft cannot. PK-NUK was 22 years old when it disappeared, well within the operational lifespan of the type. The Aviation Safety Network records the accident with the sparse notation that defines so many losses in remote regions: aircraft missing, presumed crashed, no survivors. The disappearance of Flight 6715 is a reminder that aviation's risks are not distributed equally. The same geography that makes flight necessary -- scattered islands, deep water, volatile weather -- is the geography that makes disappearance possible.
The presumed crash site lies over the Molo Strait at approximately 8.72S, 119.79E, between the islands of Sumbawa and Flores in the Lesser Sunda Islands. The strait is a narrow but deep body of water visible from altitude as a dark channel between the two larger islands. Sultan Muhammad Salahudin Airport (WADS) on Sumbawa was the departure point. Frans Sales Lega Airport (WRKG) in Ruteng, Flores, was the intended destination. The volcanic terrain of Flores rises sharply from the coast, creating the kind of complex topography that challenges low-altitude flying in poor weather. Approach the area from the south for the clearest view of the strait and the mountainous western coast of Flores.