1 flight. 1 mountain. 11 people.

11 people. 1 charter flight. Mount Bulusaraung. January 2026.
Preliminary report on PK-THT now available.

I’ve been applying my SToC framework to aviation accidents for a while now. This one is a near-perfect illustration of why the framework uses a Venn, not a list:

3 criteria. Each one a failure on its own. Where they meet? That’s where PK-THT was.

S: Safety
Minimum Safe Altitude Warning (MSAW) last updated 2015. Terrain not configured. EGPWS fired 4 times seconds before impact. The safety net activated too late. A functioning warning system is not the same as a functioning safety system. The conditions that made the warning unrecoverable were already in place.Safety net simply was not there.

T: Technology
Global Navigation Satellite System (GNSS) degraded. Crew and ATC had different position pictures. 2 parties, 1 aircraft. GNSS had degraded signal quality. FCOM is explicit: cross-check by conventional means or change navigation method. Technology could not be trusted but crew appears to have continued trusting it. This is SToC’s core technology hazard in a direct form: system signalling its own unreliability, and the reliance continuing regardless.

O: Organisational culture
11 years without an MSAW update. Not a technical failure. Just normalised tolerance, until its no longer normal. Crew flew without headsets/boom mics (violating SOP’s) while an ATC supervisor initiated a non-duty conversation while the assistant controller stepped away, leaving one controller monitoring a flight in mountainous terrain with reduced attention. Neither failure was mechanical. Both cultural.

Context is where all 3 converge
Night. IMC. Mountainous terrain. An approach where position accuracy isn’t a margin issue, it’s a prime survival issue. Good CRM would have established the MSA, but the conditions for a safe outcome had been removed long before the approach began.

+R Regulation: existed on paper. Not in practice. The aircraft was reconfigured from passenger to a surveillance 9 months before the crash. What oversight governed that transition? What updated training was required for crews operating in a new role, with new equipment, in mountainous terrain under IFR?

+RC Technology moved. System around it didn’t. 9 months from passenger to surveillance aircraft. The role changed faster than the surrounding safety architecture (training, SoP’s).

Every component lit up.
That’s not bad luck. That’s a system that had quietly removed the conditions for a safe outcome long before the approach began.

Technology is strongest here; GNSS DGR warning: a textbook SToC hazard. System was explicitly flagging its own unreliability & the crew’s position reports still didn’t match radar. That’s not a technology failure in the mechanical sense; it’s reliance continuing past the point the technology said stop.

10 people died on a mountain that was always there, in terrain that was always charted, with a warning system that worked exactly as designed.