Between the time a passenger boards an airplane and the time they disembark, there are 6 distinct phases:
Almost half of all accidents occurs during the final approach and landing stages. These are also the most devastating accidents.
Fatal accidents are also likely to occur during the climbing stage. If the aircraft left the gate with undetected faults, these may become apparent during the climb, as the first stage taking place off the ground, and could prove dangerous. If the crew believe the failure requires the aircraft to land as soon as possible, they will decide to perform an IFTB (In-Flight Turn Back). This could turn out to be difficult, however, as the aircraft is flying low and may have already lost some of its capabilities.
Most accidents and fatalities take place during the departure (take off / climb) and arrival (approach/ landing) stages. During these phases aircraft are close to the ground and in a more vulnerable configuration than during other flight phases: the crew have to deal with a high workload and reduced manoeuver margins.