The de Havilland Canada DHC-4 Caribou was designed in the 1950s for short, rough-field operations. It takes off in spaces no sensible aircraft should. It lands on grass, on mud, on anything flat enough. PK-SWW was an unusual example: a Caribou built in 1971, later modified by PEN Turbo with Pratt and Whitney Canada PT6-67A turboprop engines replacing the original piston engines, first flown in its new configuration in September 2014. Indonesia took delivery in May 2016. The aircraft entered service that September, jointly owned by the central government and the Puncak Regency authorities, purchased specifically to lower the cost of fuel flown into remote Papuan districts. It was six weeks into its Indonesian career when it disappeared.

The backdrop is politics as much as geography. For decades, Indonesian national development concentrated on Java and Sumatra. When Joko Widodo became president, he redirected attention east. Airports expanded. Subsidized pioneer flights increased. In Puncak Regency, the government bought a DHC-4 to reduce oil prices; the cost of a liter of fuel in the central highlands had long been a symbol of how little the state reached into these mountains. The Caribou was part of that answer. On 31 October, it was flying construction materials to Ilaga in the next valley, exactly the kind of work it was purchased to do.

At 09:22 local time, another aircraft picked up a signal near Jila that looked like an emergency locator beacon. Basarnas, the National Search and Rescue Agency, moved quickly. The Indonesian Air Force, the army, and the national police assembled a team with two helicopters and two fixed-wing aircraft. Three base camps were established. Then the Papua rain arrived, which is what Papua rain does, and the search was grounded. In these valleys, visibility closes in minutes. A helicopter that can reach a crash site in the morning can be weathered out of the air by noon, sometimes for days.

The wreckage was spotted on 1 November on the side of Ilaga Pass at an elevation of 12,800 feet, roughly nine nautical miles from Jila and six from Ilaga. The aircraft had burned completely. Debris was strewn across the valley, the impact severe enough that no one inside could have survived. Two helicopters carried the bodies out to Timika, where a procession was held to honor the four crew. None of them made it to 40. All four were Indonesian, working a cargo run in their own country's most difficult flying region. The aircraft had been in Indonesian hands for five months.

The Flight Data Recorder and Cockpit Voice Recorder were both missing when the site was initially worked. On 6 November, search teams recovered them. Both were sent to Jakarta for analysis by the National Transportation Safety Committee, KNKT. The interim report recommended that the operator, Perkumpulan Penerbangan Alfa Indonesia, comply with a specific Directorate General of Civil Aviation safety circular from earlier that year. Papua's flying record is difficult reading. The combination of extreme terrain, unreliable weather, marginal infrastructure, and aircraft pressed into service in conditions they were never certified for has produced an almost annual roster of losses. Aviastar Flight 7503, Trigana Air 267, and now the Alfa Indonesia Caribou all sit on the same list. Four names are now on it too.

Ilaga Pass sits in the central highlands at almost 13,000 feet, a corridor between jagged limestone ridges that regularly hide inside cloud. The standard routing from Timika requires threading such passes to reach the interior villages that have no road access and will not have road access in any foreseeable future. The Caribou, with its short-field performance and strong high-altitude engines, was one of the few airframes that could service strips like Ilaga at all. When it failed here, the failure was not just of a single flight. It was of the narrow margin on which all of this flying depends, every day, when the weather holds.