A fatal helicopter crash into the roof of a far north Queensland hotel could have been a lot worse, investigators say.
Hundreds of guests were evacuated and two people hospitalised after the "massive explosion" at Cairns' DoubleTree by Hilton in Cairns early on Monday.
The pilot died at the scene and is yet to be identified, and mystery surrounds the circumstances of the "unauthorised" flight.
Australian Transport Safety Bureau Chief Commissioner Angus Mitchell said the crash could have been deadlier given the rotor blades of the helicopter smacked into the hotel rooms, one of which had an elderly couple asleep inside.
"It's miraculous ... It certainly could have been a lot worse," he told ABC Radio.
"It's not only the enormous forces of the impact damage, but then the post impact fire that followed as well."
The two hotel guests, a man in his 80s and a woman in her 70s, were taken to hospital for smoke inhalation.
The hotel was nearly full, with almost 400 guests evacuated, and many people were still walking around Cairns at 1am, which heightened the risk of a more dangerous incident, Mr Mitchell said.
Crash investigators are probing the sequence of events, as information so far indicates the four-seater chopper was airborne for only five minutes before the crash.
Mr Mitchell said the investigation would particularly focus on the final impact and whether something other than individual fault was to blame.
Police are investigating how the helicopter was taken on an unauthorised flight.
"Flying a helicopter, getting it up off the ground isn't something that anyone could do," Mr Mitchell said.
"You do need to have someone that has quite a detailed knowledge of the helicopter itself and how to fly it."
Other lines of inquiry will include whether the helicopter was stolen, if the crash was deliberate and how fast the aircraft was flying.
Sydney tourist Veronica Knight witnessed the helicopter flying around Cairns, describing the aircraft as travelling at a very fast speed.
"It was like an army helicopter, but faster. Like a warplane, like it was going to come in and bomb you," she told AAP on Monday.
Mr Mitchell said the crash was unusual and unsettling for the community.
"Police went to great lengths to reassure the public here that they believe it is a one-off incident and there's nothing else behind this, because things like this are unsettling," he said.
"We only have to look into the past history around planes into buildings and where that can potentially lead us."
