Australian air safety authorities are warning a fatigue crack appears have caused a Cessna 210's wing to snap off before it crashed in northern Queensland, killing two men.
The pilots were about 90 minutes into a low-flying geological survey operation near Mt Isa when they crashed on May 26, the Australian Transport Safety Bureau (ATSB) says.
Pre-existing fatigue cracking in the Cessna 210's wing spar caused an "overstress" on the plane's right wing during the flight, the bureau said on Friday in an update on their investigation into the crash.
The wing broke off about 60 metres (200 feet) above the ground "resulting in a rapid loss of control and subsequent collision", investigators said.
They have notified the Civil Aviation Safety Authority, the US National Transportation Safety Board, the aircraft manufacturer and operator of the initial finding," ATSB executive director Nat Nagy says in a statement.
The ATSB is working closely with all of them to ensure that safe operation of Cessna 210 planes continued, he said.
The Cessna aircraft was built in 1976 and had flown 6000 hours in the six years since it was modified for geological survey work in Australia six years ago.
The plane had a permit for the installation of wingtip fuel tanks and a non-standard engine, but is not known if these were fitted.
