As of 2012, we have identified 206 men from the Hellbirds who died in WWII from all causes.
Many of these deaths were accidents due to engine problems, mechanical failures, fire, lack of fuel, weather or just flying in uncharted, mountainous areas. Remember, there were no satellites, GPS devices or any other advanced navigational support that we take for granted today.
Takeoffs were very hazardous. Most B-29s were rated by Boeing at 120,000 pounds, but routinely grossed out at 130,000-135,000 pounds, when fully loaded with bombs and fuel.
16 of the 206 deaths were POWs executed by the Japanese.