On September 8–9, the 2011 Southwest blackout affected parts of Southern California and Arizona, as well as parts of northwestern Mexico. The failure initiated after maintenance of a 500 kV line brought it offline, and subsequent weaknesses in operations planning and lack of real-time situational awareness at multiple power stations led to cascading outages. Power restoration was generally effective, but also affected by communication issues, with 100% power restoration occurring from 6–12 hours depending on location. Over five million people were affected.