A Raymond Terrace community Facebook page was flooded with questions from worried residents asking what the “insanely loud noise” was just before 10pm on Thursday.

“First time in 30 years living in the Terrace I have heard anything like it,” Margaret Kirby wrote.

Several residents said they went outside trying to find the source of the noise but could see no jets flying. One posted they feared it was a tidal wave, another a UFO and someone said they could hear it from Thornton. 

The Department of Defence solved the mystery on Wednesday revealing that it was maintenance personnel from Williamtown RAAF Base conducting high-power engine runs in support of aircraft fuel system testing on an F/A-18 Hornet.

But angry residents were left wondering why the testing had to be conducted so late at night and why no warning was given.

A Williamtown resident said it was “typical” of Defence “not caring” about the community.

“This ungodly noise that scared half the neighbourhood out of bed all for some testing, it’s just typical of Defence’s attitude to this community,” he said. “Once again it shows Defence is nothing but the neighbours from hell.”

A Department of Defence spokesman said to “mitigate the noise impact on the local community” the aircraft’s exhaust was “pointed away from more populated areas”.

“This type of testing is usually conducted in a high-power engine run facility in order to contain the sound emitted during testing,” he said.

“Due to competing maintenance priorities the testing facility was not available in this instance.”

Residents initially feared the noise was coming from a F-35A Joint Strike Fighter that will be based at Williamtown.