AIR traffic controllers did not pass on a significant weather warning received more than two hours before a plane carrying cattle baron Peter Menegazzo was ripped apart by thunderstorms in regional NSW last year.
Menegazzo, 62, his wife Angela and two pilots died when thunderstorms in a massive front apparently ripped off part of the plane's wings and most of its tail section as it flew from Archerfield in Queensland to Swan Hill in Victoria. The accident left a 4km trail of wreckage as the aircraft broke up near the NSW central western town of Condobolin.

Pilot Anthony Gobel's attempts to avoid bad weather took the 23-year-old Piper Chieftain, which was not fitted with weather radar, 54km off its planned track before it disappeared at 1.50pm on December 2.

Crash investigators say Gobel obtained the appropriate weather report, issued at 9.33am, before taking off at 11.22am, and was aware there were occasional thunderstorms and a surface trough moving through central NSW.

But the pilot was not given, and did not request, an amended report issued at 11.30am indicating the frequency of the thunderstorms had increased east of a line from Bourke in far western NSW to Griffith in the Riverina.

He also did not receive a SIGMET, an en-route warning about weather that may affect aircraft safety, reporting frequent thunderstorms in the flight path of the Chieftain and within 111km of a line from Cobar to Wagga Wagga.

"The investigation has established that SIGMET SY01 was received by Airservices at 11.27am," said an interim Australian Transport Safety Bureau report, released yesterday. "A review of recorded audio data confirmed the pilot did not receive SIGMET SY01 or request weather updates from air traffic services staff while en route."

The report said a severe storm front was passing through the area at the time of the accident and that weather radar showed storm cells close to the aircraft's last reported position.

"There was evidence that immediately before the accident, the aircraft was likely to have been surrounded to the east, west and south by a large complex of storms," it said.

Gobel was an experienced commercial pilot with a grade 1 flight instructor rating and 4600 hours flying time, including 1000 hours on the Piper Chieftain. Fellow pilot Derek Mostyn, who was travelling as an observer to gain experience in the aircraft, had about 1560 hours in the air.

Both pilots were experienced enough to control the aircraft if the weather had forced them to bank steeply.

Investigators will look at whether the aircraft should have been provided with a hazard alert as part of several issues for their continuing inquiry.

But ATSB aviation safety deputy director Julian Walsh said there were conflicting references in the Airservices manual about whether an alert had been required, and the issue was complex.

"There are probably no black-and-white answers on that at this stage of the investigation," he said.

"It's still a bit early."