David and Jean Hewitt were on the caravan park which adjoins Caernarfon Airport, when the crash happened yesterday morning.
They said the plane clearly appeared to be coming in too slowly and too low, and didn't reach the runway, but clipped trees and flipped over.
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It is going to stay fine and dry through the night with light winds.
It is going to stay fine and dry throughout.
There have been four deaths on the M4 in just the last eight days following crashes between Swansea and Newport.