According to New Zealand investigators, the May 2004 crash of a Swearingen Metro was caused by an in-flight upset which developed into a spiral dive. The crew did not recover control and the aircraft became overstressed and broke up, to fall in pieces about rural farmland near Stratford. Both crew were killed and the aircraft and cargo destroyed. The crew was balancing fuel between tanks, flying the aircraft at an excessive sideslip angle with the rudder input trimmed, while on autopilot. The autopilot capability was exceeded and it disengaged, precipitating the upset.