A pilot and passenger were killed Thursday when a light aircraft nosedived into a small private lake in a northern suburb of London. The plane was a Yak 52, used as a trainer for practicing aerobatics, a news Web site, This is Total Essex, said. Three planes were flying in formation, with the other two landing safely at their base. Essex Fire and Rescue responded to the lake in Maldon, the Essex Enquirer reported. Witnesses said the plane crashed into the lake nose down and came to rest with its tail about 10 feet below the surface. Dave Barritt, incident commander for Essex Fire, said the plane that crashed appeared to clip a tree, the BBC said. Officials said light planes practicing aerobatics and formation flying are a common sight in the area before summer air shows.