Trista Applebee embarked on a private joy flight on the Gold Coast on June 5, 2019, as a "treat" the day before her 31st birthday.
Martinus Van Hattem was the pilot, flying his Yak-52 warbird.
They took off from Southport Airfield around 9.45am, but they didn't make it back.
The aircraft crashed into waters off South Stradbroke Island.
Parts of the wreckage were found that afternoon and the bodies of Mr Van Hattem and Ms Applebee were found in the following days.
Ms Applebee's partner Glen Wilson gave evidence on the first day of the coronial inquest into the deaths.
He told the inquest he had organised the half-hour birthday flight for Ms Applebee, as a "cost share" agreement with the private pilot.
He was due to go for a fly with Mr Van Hattem himself when they returned, Mr Wilson said.
"I'd seen him (Mr Van Hattem) around," he said.
"I got his phone number to make arrangements to go for a fly with him."
Mr Wilson said he raised the alarm when the aircraft didn't return, calling authorities and nearby airfields.
"After 45 minutes, I thought it was a bit funny that they weren't back yet," he said.
"I thought maybe because it was her birthday, he might've extended the flight."
Mr Wilson told the inquest he and Mr Van Hattem had discussed the possibility of doing some aerobatics with Ms Applebee onboard.
"If she was comfortable at the end of that flight, flying at the correct altitude, in the acrobatic area, [in] a gentle loop," he said.
Flight aerobatics
Counsel assisting the coroner Ian Harvey said the joy flight was intended as a "treat" for Ms Applebee ahead of her birthday.
Mr Harvey told the inquest Mr Van Hattem obtained a private pilot licence in 2014, but had held a pilot certificate, issued by self-administrative organisation, Recreational Aviation Australia, since 1999.
"He acquired his aircraft (the Yak-52) in about July 2018," he said.
"He obtained an aerobatic flight activity endorsement on January 17, 2019.
"By early June 2019, he'd accumulated about 40 hours (in the aircraft)."
Mr Harvey said one of the issues that would be considered in the inquest was the level and adequacy of Mr Van Hattem's pilot training to undertake aerobatic manoeuvres.
"It will clearly emerge from the evidence Mr Van Hattem enjoyed flying and enjoyed aerobatic manoeuvres in his aircraft," he said.
Coroner Carol Lee will also consider the adequacy of oversight and regulation of warbird flying operations and the airworthiness and maintenance of the aircraft.
The inquest is expected to continue until Thursday.
