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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Variable cloud and clear spells overnight with isolated showers mainly in the north.
Becoming drier and brighter from the northwest during the day, but with the risk of scattered, locally heavy, showers developing later.