£20m RAF Hawk jet that crashed in a fireball yards from a caravan park was flying without its fuel cap

Ground crew are reportedly considered responsible for the missing cap, which investigators are said to treat as 'a significant part' of the inquiry. The Hawk T2 caught fire as it departed RAF Valley on Anglesey on September 23, during a test flight following repairs. An experienced pilot and a trainee managed to steer the aircraft away from residential areas before both ejected, sustaining only minor injuries. The RAF said it would be 'inappropriate to comment further'.

One source asked: 'If a fuel cap can be left off, what else can be?'

After 20 seconds airborne, the jet went into a spin and came down on farmland near Afallon Caravan Park.

Other sources point to a 'major engine failure' as a possible cause.