The cause of the first two losses continues to be unknown as the wreckages have never been recovered. It turned out that the third loss on 22 April was not due to enemy action, but was traced to a failure of a hydraulic control-valve rod for the horizontal stabilizer which caused the aircraft to pitch up uncontrollably. Further inspection of the remaining fleet of F-111As revealed 42 aircraft with the same potential failures. It is speculated that this failure could also have contributed to the two earlier losses had the failure caused a pitch down while at low altitude.