The search for a couple whose plane crashed at high speed in waters off Moreton Island has been called off.

Key points: The male pilot made a mayday call to air traffic control before the plane went down

The male pilot made a mayday call to air traffic control before the plane went down A significant amount of debris from the plane has been found scattered over a large area

A significant amount of debris from the plane has been found scattered over a large area The crash will be investigated by the Australian Transport Safety Bureau

The 70-year-old male pilot and his 52-year-old wife, from Wakerley in Brisbane's Bayside, left on a scenic flight in the hired plane around 3:30pm on Wednesday.

The flight was expected to return to Caloundra after flying over the island but a mayday alert was sent an hour after take-off.

Water Police, the Redland Bay Coast Guard, Bribie Island Volunteer Marine Rescue, a jet, two rescue helicopters and five fishing trawlers searched in the area until midnight amid rough seas and storms.

They continued at first light on Thursday.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 1 second 1 m 1 s Mayday call from light plane off Qld's Moreton Island.

A significant amount of debris from the plane has been found, including a wheel and sheets of metal from the aircraft's fuselage, scattered over a large area.

"All evidence indicates the aircraft ditched into the water at high speed," an Australian Maritime Safety Authority spokesperson said in a statement.

"AMSA has received expert medical advice that the impact would not have been survivable.

"AMSA extends its sincere condolences to the family of both people on board during this difficult time."

A rescue helicopter searches the water off Moreton Island. ( ABC News )

TV traffic reporter Ben Mihan said he heard the call for help while flying near Redcliffe.

"There was only one mayday call coming out from this Cessna … an older gentleman making the mayday call, it was very simple, just the call sign and the mayday call — there was nothing else other than that," Mr Mihan said.

Mr Mihan, from Australian Traffic Network, heard the mayday call. ( ABC News: Dean Caton )

"The air traffic controller tried to reach him, but it just went totally silent and that's when we knew something terrible went wrong."

Mr Mihan said they took a look around Moreton Bay before having to land their helicopter back at the airport.

"Obviously we were quite close to where the plane went down — we weren't sure where it went down — so I started … having a look out for fire coming from the land, if it hit the land, seeing smoke, whether there was debris on Moreton Island that we could see, but unfortunately we couldn't see anything," he said.

The plane, which was available for hire, crashed in Moreton Bay on Wednesday afternoon. ( Facebook: Inspire Aviation )

"I assumed the aircraft went … down on the opposite side of the beachside where we couldn't see.

"I'm a pilot myself … I've flown that route quite often and know it very well and it's just a tragedy to see a plane's gone missing.

"I'm sure many people are feeling the same shock as I am."

Inspector Craig White said the couple's next of kin had been informed.

The aircraft was owned by Michael and Amy Rowe of Little Mountain who hired it out to the couple.

"We are absolutely heartbroken for the family," Ms Rowe said.

Rough weather hampered the search on Wednesday night. ( ABC News )

The air crash will be investigated by the Australian Transport Safety Bureau and police will assist.

McDermott Aviation owner John McDermott said two of the company's helicopters were involved in the search.

He said AMSA experts had provided crews with a grid area to search and they had been looking out for people that might be swimming or waving in the water or any signs of a wreckage.

Police had been scouring the Moreton Island coastline on foot.