1. Air Traffic is growing causing more and more aircrafts in one airport. This could lead to fatal accidents like The KLM and Pan Am(I think Pan Am) Colliding with each other on the runway.
2. Turbulence not being able to be detected. There has been a few incidents of people dying due to turbulence such as United Airlines flight from Narita. One person died due to severe neck wounds.
3. Pilots. These people play a big factor. Alot of planes over shoot runways. This could cause a fire in the cabin causing loss of life. Also Mis guidence. Such as the SQ flight. The pilot took of on the wrong runway.
4. Weather. Fog cover over the airport causing planes not being able to see very far.
Hopes these points help
PS They are just examples i don't want people biting my head about what i said about pilots.