The 2009 collision between the defunct Russian satellite Cosmos-2251 and active Iridium-33 produced over a thousand pieces of space debris and is considered one of the worst known debris-generation events in Earth orbit.
Iridium changed its operations after the 2009 collision of the Iridium 33 satellite with the defunct Russian satellite Cosmos 2251 to work more closely with the U.S. Air Force for updated collision-risk information.