Four US marines also died in the crash on the Kuwait-Iraq border on March 21st 2003.
Today's coroner's report says there is "no evidence whatsoever" to support claims that pilot error was behind the fatal crash.
Mr Walker, who has previously clashed with the Pentagon over the death of Lance Corporal of Horse Matty Hull, criticised the US for making his job "more difficult" and the experience of grieving families "more harrowing".
A British board of inquiry report initially concluded that the crash was due to a mechanical fault, but later the Ministry of Defence aligned itself with the US' take on events.
Colour Sergeant John Cecil, 35; Captain Philip Guy, 29; Marine Sholto Hedenskog, 26; Warrant Officer Second Class Mark Stratford, 39; and Major Jason Ward, 34, of the Royal Marines were the first British troops to die in the Iraq conflict.
Operator Mechanic Second Class Ian Seymour, 29; Sergeant Les Hehir, 34; and Lance Bombardier Llywelyn Evans, 24; all of Third Commando Bridage, were also killed in the March 21st 2003 crash.
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