Historically, many accidents and catastrophes have resulted from microsleep episodes in these circumstances. For example, a microsleep episode is claimed to have been one factor contributing to the Waterfall train disaster in 2003; the driver had a heart attack and the guard who should have reacted to the train's increasing speed is said by his defender to have microslept, thus causing him to be held unaccountable. On May 31, 2009, an Air France plane (Air France Flight 447) carrying 228 people from Brazil to France crashed into the Atlantic Ocean, killing everyone on board. The pilot of the plane reported "I didn't sleep enough last night. One hour – it's not enough," handing over control to the two co-pilots who did not respond appropriately when the plane was in distress. Perhaps the most notable example was the Chernobyl nuclear reactor accident in Ukraine in April, 1986. The reactor began to overheat at about 1:30am because critical cooling valves were shut off. The shiftworkers, sleep-deprived and likely experiencing microsleeps with consequent reduced decision-making ability, mistakenly disabled the cooling system, causing the reactor to overheat. As a result, there was a destructive explosion, resulting in numerous radiation-related injuries and casualties.