NAA: MP1049/1, 1918/066, page 35 is a copy of a report from Constable A. E. Duvanel of Korumburra Station, Victoria Police. Duvanel gives a blow-by-blow account of his conversation at 8pm on 2 May 1918 with Mr Sandman of the Kongwak butter factory about 'a bright light high up in the sky', which had been there for about one and a half hours, 'moving backwards and forwards in the same place', in the direction of Morwell (meaning to the northeast). Duvanel, another constable and employees from the Post Office all have a look, noting that 'with the naked eye it appeared to move up and down but with the aid of a powerful field glass it could at once be seen it was only a star, which would light up bright and was continuously twinkling'.
From the conversation that passed on the telephone it was absolutely certain these people were watching a star in the sky and imagined it an aeroplane.
Duvanel's conclusion seems sound, though which 'star' it actually was is harder to figure out (Arcturus was my first guess, but it was just rising at 8pm and couldn't have been seen for 90 minutes before then; Mars maybe, though no colour is mentioned and planets don't twinkle as much as stars).
But the real puzzle here is who, exactly, claimed to have seen an aeroplane? In my article I say it was 'employees' of the butter factory, but while that's possible, reading the report again I think that's a faulty inference. (Duvanel doesn't even say Sandman was at the factory when he made the call, just that he was 'of' it; I wouldn't have thought that butter would be made in the evening, though it's possible that a manager would have been there after hours.) Duvanel says that Sandman told him on the phone 'that an Aeroplane was over Kongwak', but when asked 'if he saw an aeroplane' replied 'no one has seen one', only the bright light in the sky. Then there's the 'communication' of a Mr Tate that 'an aeroplane was seen at Kongwak', but Duvanel points out that Tate was at the station two days later and never made mention of it. So nobody is recorded as having claimed to have seen an aeroplane, or even that anybody else saw one -- yet it was reported as an aeroplane sighting. My best guess is that Sandman was reporting a rumour that was passing around Kongwak that an aeroplane was overhead, but didn't see it himself; Tate was either passing on the same rumour or possibly had seen it himself, but made his report directly to military intelligence rather than through the police; this prompted a request for information from Melbourne and so Duvanel had to make this belated -- six days after the event -- and somewhat exasperated report of what he was completely sure was nothing at all.