Nearly 40 years ago, Phil Tindale believes he witnessed what can only be described as an air battle between two UFOs — which ended with one crashing to earth.

It was about 9.30pm on Thursday, February 7, 1980, and he was at home in the South Australian town of Aldgate when his twin brother Rob called out from his bedroom, “Phil, come and check this out.”

From their window looking down the valley towards Stirling, about 20 minutes southeast of Adelaide, the 10-year-olds saw a bright yellow object “bobbing around” just above the tree line, about 1km away.

After a few minutes, Phil says a second, slightly larger object appeared emitting a red light. In what he describes as almost cartoon-like motion, it “zoomed up” to the yellow object, stopped and reversed, then did it again “as if to prompt a reaction”.

The yellow object then “took off” with the red object in pursuit. They zigzagged across the sky like two “blowflies”, changing direction instantly with no apparent inertia and covering distances he later estimated to be up to half a kilometre in less than a second.

Throughout the “chase”, which Phil says lasted several minutes, the yellow object would periodically stop in mid-flight and shake back and forth “as if caught by some invisible force” before freeing itself.

Neither object made any noise. Eventually the yellow object sped off and disappeared behind a hill, and the red object also vanished. In total, he believes the entire sighting lasted about 15 minutes.

Rob Tindale confirmed his brother’s account.

“Certainly there were two lights, one appeared to the chasing the other, they both dipped below the horizon,” he said.

“It was a very memorable thing.”

The same night, a local farmhand, 21-year-old Daryl Browne, reported seeing a “speedboat-shaped yellow thing” like a “half moon” crash into some trees near the horse farm where he worked — in the exact area where the brothers last saw the object.

According to newspaper reports, Mr Browne told police he was watching TV that night when his dogs began howling. “And then I heard the trees smashing,” he said.

“I locked the kids inside and went outside with a torch.”

Mr Browne shone the flashlight into the trees and saw the object, which was “about 25 to 30 feet long” and was not emitting and sound or light. He called police but the object had disappeared by the time they arrived.

At the time, police told media only that there were unexplained broken branches and no other physical evidence. Mr Browne was interviewed by investigators from UFO Research South Australia the next day, who published a report in that month’s UFO Research Australia newsletter.

For Phil, 49, the strange sighting was nothing more than a “campfire story” for the next 30 years or so. It wasn’t until around 2009 that he decided to investigate further, revisiting the scene of the crash and delving deep into the UFO topic.

He believes their sighting is unique, saying he has been unable to find virtually any other reports of “conflict” between UFOs. He says he is “100 per cent” convinced what he saw was extraterrestrial, and not military aircraft.

“Over the years I’ve done lots of reading but also personal investigation, contacting people one to one. There are loads of people out there who just don’t report it, don’t talk about it,” he said.

“Not everyone has a fantastically compelling sighting, often it’s just lights in the sky, but there are significant numbers of sightings where there is an object that is so far beyond our capability it has to be extraterrestrial.”

Rob said he was probably a bit more “conservative” than his brother about certain aspects of the UFO topic, but if he had to guess what it was they saw that night, “I would tend on the extraterrestrial side”.

“Certainly in the ‘80s and even these days, the fact that the objects made these quick, jerky motions, couldn’t have happened with the technology we’ve got,” he said, adding that it hadn’t particularly affected him. “It wasn’t like a close encounter, it was just seeing some lights in the sky — like watching a meteorite.”

Interest in the UFO subject has been revitalised in the past two years since The New York Times published a bombshell article revealing the existence of a Pentagon UFO study program. In the same article, a former high-ranking US Navy fighter pilot recounted chasing a “Tic Tac”-shaped UFO.

Phil said commander David Fravor’s description of the object’s movement resembled what he saw. “The instant acceleration, nothing can do that unless you’ve mastered the force of gravity, not using any conventional propulsion,” he said.

He says he has “considered everything” in terms of other possible explanations for what he saw but “the movements of the craft” were simply impossible using “any conventional propulsion”.

“There must be a million people like me,” who have seen things but don’t report them, he adds. In South Australia, at least, Phil is not alone. UFO sightings have been reported in the state since the early 20th century, but surged during the Cold War.

The most famous case was the 1988 incident with the Knowles family, who said they driving along the remote Nullarbor Plain when a large glowing object “like a big ball” chased them and lifted their car off the ground.

Paul Curnow from the South Australia Astronomical Society said it was still common to get from several dozen to hundreds of UFO reports a year in South Australia.

“Probably for every 10 cases you get, nine can be explained in mundane terms,” Mr Curnow told the ABC last year. “Quite often people report a little silver dot in the sky (and it) turned out to be an aircraft. A lot of these things like planes, satellites, planets, even searchlights sometimes, can all add to what people are reporting.”

frank.chung@news.com.au