A helicopter crash that killed four people in Missouri, Midwestern America, was partly caused by the pilot sending text messages to a friend.
The pilot of the emergency medical helicopter sent and received text messages just before the 2011 crash.
US National Transportation Safety Board investigator Bill Bramble told Bloomberg that texting increased lack of attention and errors, but the board is yet to assign a probable cause for the accident.
NTSB Chairwoman Deborah Hersman said: "This investigation highlighted what is a growing concern across transportation - distraction and the myth of multi-tasking. When you are operating heavy machinery, whether it's a personal vehicle or an EMS helicopter, you need to be focused on the task at hand: transportation, safe transportation."
According to Gadling, the pilot sent and received 20 text messages during the flight. He also told a colleague that he hadn't slept well the night before and had failed to refuel the helicopter before departure.
The helicopter crashed in a field as it was approaching an airport for the pilot to refuel, killing the pilot, a paramedic, a nurse and a patient died.
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