|Time||6 April 1966|
|Location||Westall High School and The Grange in Clayton South, Victoria, Australia|
|Also known as||Westall High School UFOs|
At approximately 11:00 am on Wednesday, 6 April 1966, students and a teacher from Westall High School, now Westall Secondary College, reported seeing a flying object, described as a grey (or silvery-green) saucer-shaped craft with a slight purple hue and about twice the size of a family car. According to the students, the object was descending, overflew the high school, and disappeared behind a stand of trees. Approximately 20 minutes later the object reportedly reappeared, climbed at speed and departed towards the north-west. Some accounts describe the object as being pursued by five unidentified aircraft.
Australian newspaper The Age described it as a weather balloon: "Object Perhaps Balloon – An unidentified flying object seen over the Clayton-Moorabbin area yesterday morning might have been a weather balloon. Hundreds of children and a number of teachers at Westall School, Clayton, watched the object during morning break. The Weather Bureau released a balloon at Laverton at 8:30 am and the westerly wind blowing at the time could have moved it into the area where the sighting was reported". The newspaper also said a number of small aeroplanes circled around it. However, a check later showed that no commercial, private or RAAF pilots had reported anything unusual in the area.
According to Keith Basterfield, a runaway balloon from the HIBAL High-altitude balloon project used to monitor radiation levels after British nuclear tests at Maralinga is a likely explanation. Basterfield located documents in the National Archives and former Department of Supply indicating a test balloon launched from Mildura may have been blown off course "and came down in Clayton South in a paddock near Westall High School, alarming and baffling hundreds of eyewitnesses, including teachers and students". Basterfield said HIBAL balloons had a white silver appearance and featured a parachute and gas tube trailing from the top, which is consistent with witness descriptions of the object. There were also reports that after the incident, "men in suits" cautioned witnesses not to discuss details of the secret government exercise.
According to skeptic Brian Dunning, "the weather balloon is a likely explanation for the first half of the event". Dunning suggested a nylon target drogue, like a wind sock, towed by one plane for the others to chase and known to be in use by the local RAAF at the time, was "at least one very reasonable possibility for the second half". Dunning added, as years have passed, "descriptions of what was actually seen have now become diluted with made-up descriptions by an unknown number of students who didn't see anything, and there's no way to know which is which".
On 21 January 2016, Channel 10 (Australia) program Studio 10 screened a segment titled: "21 Jan – Melbourne UFO Mystery: 50 Years On" which included live interviews with witnesses who were children at the local school in suburban Melbourne in 1966.
- A witness reunion was held at Westall Tennis Club Hall, on 8 April 2006, to commemorate the 40th anniversary of the incident.
- The City of Kingston created a children's play space, Grange Reserve UFO Park at The Grange Reserve in Clayton South Melway. The park features a silver UFO with red slides to reflect the 1966 Westall UFO Incident.
- "Flying Saucer Mystery, School Silent" (14 April 1966 p. 1 and 21 April 1966 p. 1-2). The Dandenong Journal.
- Foster, Ally (8 August 2018). Weir, Sam (ed.). "Audio reveals creepy details of Australian UFO mystery RARE audio of a physicist discussing one of Australia's greatest unsolved UFO cases could shed light on the baffling events of the 1966 incident". Herald Sun. Melbourne, Victoria, Australia: The Herald and Weekly Times (News Corp Australia/News Corp). Archived from the original on 7 August 2018. Retrieved 2 July 2021.
In 1966 over 300 children and staff from a Melbourne school reportedly witnessed multiple UFOs silently flying through the sky before landing in a nearby field. It is the largest mass UFO sighting in Australia yet hardly anything was reported on it at the time...
- Perkin, Graham; Macdonald, Ranald, eds. (7 April 1966). "Object Perhaps Balloon". Main section. The Age. CXII (34604). Melbourne, Victoria, Australia: David Syme & Co. Ltd. p. A6. ISSN 0312-6307. Retrieved 2 July 2021 – via Google Newspapers.
- Dunn, Mark (2 October 2005). Weir, Sam (ed.). "Westall 'UFO' incident was actually government radiation testing, reports reveal". Herald Sun. Melbourne, Victoria, Australia: The Herald and Weekly Times (News Corp Australia/News Corp). Archived from the original on 4 February 2016. Retrieved 2 July 2021.
- Dunning, Brian. "The Westall '66 UFO". Skeptoid.com. Skeptoid. Retrieved 23 March 2021.
- Horton, Adrian. "'It's not a question of belief': the film examining government UFO records". the guardian.com. The Guardian. Retrieved 24 March 2021.
- Ronn, Florenz (17 January 2006). "The 1966 Westall UFO incident". 774 ABC Melbourne (www.abc.net.au/radio/melbourne/).
- "Academic throws light on 40-year-old UFO mystery". The Age. 2 October 2005. Archived from the original on 21 June 2021.
- "The Grange Reserve (UFO Park)". kingston.vic.gov.au. Kingston City Council. Archived from the original on 21 June 2021. Retrieved 24 March 2021.
- Sharpe, Matthew (3 April 2016). "Westall '66: 50 years on, still stranger than fiction". theconversation.com with Shane Ryan (The Conversation Trust (UK) Limited). Deakin University. Retrieved 20 June 2021.
- Weise, Derek (27 October 2018). "Westall Missing Witness Interview with UFO Research Queensland - EXCLUSIVE". www.youtube.com (Sheryl Gottschall, UFO Research Queensland). Retrieved 20 June 2021.
- Westall '66: a suburban UFO mystery A MASS UFO SIGHTING A FORTY-FOUR YEAR CONSPIRACY. A MAN SEEKING THE TRUTH Film written By Rosie Jones, with Shane Ryan; Produced by Carmel Mcaloon