Thousands thought it was an earthquake, others thought it was a bomb. Buildings shook, windows rattled, dogs howled.
There were no report of damage, but a mystery boom that rocked a 142km stretch of the coast in south-east Queensland left lots of worried residents in its wake.
Earthquake sensors did not register a disturbance, even though the 15-second "boom" hit thousands of homes between Buderim and North Stradbroke Island.
Earthquake monitoring centres were flooded with calls that a tremor had hit just after 3.30pm, but no damage was reported.
Last night the RAAF admitted that one of its F-111s had gone supersonic east of Ballina in NSW. But they played down the chances that the jet was cause of the boom.
RAAF Wing Commander Rob Lawson said the F-111, flying at 160m, finished its manoeuvre 100km off the coast at Beenleigh.
He said he could not rule out the possibility that the jet had caused the "tremor". But "we go supersonic there all the time and people in Brisbane don't ever notice it," he said.
Air traffic control agency Airservices Australia said last night there was an area of air space off the coast where military aircraft were permitted to fly faster than sound.
Spokesman Richard Dudley said while that area did not extend as far north as Bribie Island, it was possible given certain weather and wind conditions that the sound of a sonic boom might travel some distance.
"However, that would not explain vibrations people reported experiencing," Mr Dudley said.
Relieving Moreton Island ranger Scott Rogers said he was in his office when the whole building began to shake.
Stradbroke Island resident Mark Davis said his TV shook and his dogs bolted when the plane flew over his home yesterday at Point Lookout yesterday.
"The dogs were sitting on the loungeroom floor and they freaked, jumped up and took off out the door," Mr Davis said.
Bongaree resident Darren Jellick said he felt an "enormous shudder and heard a loud bang" while working at Bribie Island. "It was the sort of sound you hear when a military bomb blows up," he said.
Bribie Island's Rod Bennett was shaken from sleep.
"I was sure someone was trying to break into the house. It was a really violent shaking of the windows, I thought they were going to break," Mr Bennett said.
