According to research conducted by Boeing into commercial flights between 2007 and 2016, 48% of fatal crashes occurred during the final descent and landing. Take-off and the initial ascent represent the second-most-deadly portion of a flight, or 13% of fatal accidents. These stages are sometimes referred to as the "plus three minus eight" rule, meaning that a majority of plane crashes take place during either the first three minutes or the last eight minutes of a flight.