Westall mass UFO sighting

Westall high school, 11am, 6th of April, 1966, Australia

A round, silver object about the size of a car with a metal rod sticking up was silently flying through the sky before landing in a nearby field. A few minutes later onlookers watched, as it lifted off and was pursued by five small cesna type airplanes. Over 300 children and staff from a Melbourne school reportedly witnessed the object. The planes tried to surround the object as more people began gathering to watch the scene. When the planes got too close, the object would slow down, then rapidly accelerate and move away. This reportedly went on for about 20 minutes. Then the craft
ascended in a north-westerly direction.

Some witnesses claim the UFO left a circle of scorched grass in the field where it landed.
The area was cordoned off and people in camouflage gear took charge of the paddock. Witnesses reported that there were at least 30 government officials at the site.

The government tried to cover up the incident and stop witnesses from talking. It is believed the Headmaster was threatened by government officials. He told the children they would be severely punished and staff they could lose their jobs if they mentioned it to anyone.
Several witnesses also claim that sharply dressed men in black suits visited them and warned them from speaking about the incident.

Some believe that it was a test balloon launched from Mildura which may have been blown off course. Balloons were created to monitor atmospheric radiation levels caused by the Maralinga nuclear tests. These baloons are set up with sophisticated sensors and appear silver in color, when in flight.
There are also those that believe it was an experimental aircraft created by the Airforce or a secret government or military agency.

There are no files on the incident found in either police or military records and no official has come forward to discuss the incident. Channel 9 television did a report about the event but the tape was removed from their library and never returned.

Hmm! What do you think?

UFO?
Balloon?
Experimental air craft?