What happened

A lightning strike disabled one of the limited number of 500 kV transmission lines on the Ungaran-Pemalang corridor connecting central and western Java on 4 August 2019. With insufficient redundant east-west transmission capacity, the remaining line became overloaded and automatically tripped, cascading into a widespread blackout across Jakarta and large parts of Java that affected an estimated 21.3 million people, beginning around 11:50 local time and lasting roughly nine hours in most areas, with some areas not restored until the following day. State utility PLN initially attributed the outage to gas-turbine disruptions at the Suralaya power plant before correcting its explanation to the transmission-line failure, and issued a public apology. Four deaths and eight fires — the fires likely linked to candle use during the outage — were reported in local media, alongside disruption to Telkomsel, Indosat, XL Axiata, Tri and Smartfren mobile networks. Estimated economic losses reached roughly Rp 90 billion. Jakarta's governor made the city's TransJakarta bus and MRT rail services free for the remainder of the day to ease the disruption. This was an accidental weather-triggered transmission failure, not an attack.

When cited sources give different casualty, damage or spill figures for this event, they’re reported side by side above rather than merged into one number. See how confidence levels work.