I'm surprised it has not been picked up here, reported on AVH. Incident happened 30 August:
An American Airlines Boeing 757-200, registration N177AN performing flight AA-213 (dep Aug 29th) from Miami,FL (USA) to Brasilia,DF (Brazil), was enroute at FL350 about 160nm west of Caracas (Venezuela) when the aircraft lost more than 7500 feet within a minute. The crew recovered the aircraft below FL275, then radioed "We lost altitude due to severe turbulence and are climbing back to FL350".
It does not sound like a controlled descent... Anybody in a position to enlighten us ?