Canberrans may have thought an air force plane was set to land in their backyards on Thursday morning.
Several residents in the suburb of Chisolm were left spooked when a jet began circling low over the area. The plane was also reported to have flown over parts of North Canberra.
"At first it was so low we thought it was looking to land because it was going to crash," one Chisolm resident, who declined to be named, said.
The woman said she and her daughter were unable to identify the grey plane and were "freaked out" by how low it flew over their home.
"Normally when they have some sort of fly over they let us know, it was so low we thought it was going to land on us," she said.
But far from conducting a training exercise, the C-17A Globemaster III was conducting a fly-past to mark the Australian Defence Force Academy graduation parade at Campbell.
The "giant" transport aircraft conducted two fly-pasts of the parade down to an altitude of just 90 metres, according to RAAF's website.
A defence spokesperson confirmed the plane was part of the ceremony and the department was investigating why the community was not warned of the fly-over.
"As with standard practice, Defence issued a noise alert prior to the event so local media could inform residents," the spokesperson said.
"On this occasion it would appear a technical glitch has prevented this alert from reaching the intended recipients.
"Defence is trying to determine the cause of this error and regrets any concern today's activity may have caused."
According to the RAAF's website, "Royal Australian Air Force fly-pasts are conducted within strict limitations".
"Residents in the wider Canberra area may notice the aircraft 'holding' as it prepares for the fly-pasts.
"This activity is subject to variables such as weather or operational availability, and may be cancelled at short notice.
"Safety and reducing noise effects are vital considerations in planning for, and the conduct, of flypast activities."
The C-17A is part of a fleet of six from the RAAF Base Amberley, west of Brisbane.