Mr Jennings was one of three people killed when their aircraft crashed near Cloncurry in the state's northwest while conducting scans for fires on Saturday.
The Disaster Victim Identification Unit and Australian Transport Safety Bureau investigators are due to arrive at the remote site on Monday.
"We are so heartbroken and need answers," his mother Denise Jennings told Nine Network's Today Show on Monday.
Ms Jennings said her only son was working for Victorian-based aerial firefighting company AGAIR just months after graduating from a Boston university with an engineering degree.
"He just came (to Australia) to help out," she said.
"We do (have questions) because he told us that it was safe, that he would be nowhere near the wildfires.
"(He said) he would be up in a plane with the thermal camera mapping out where the hot spots were."
The aircraft was conducting line scans for fires in the region and was travelling from Toowoomba to Mount Isa when it crashed.
After workers at a nearby mine raised the alarm, a rescue helicopter spotted the wreckage and officers arrived on the scene, confirming all three on board had died.
"Will was doing what he always did - helping people," his father Joseph Jennings told the Today Show.
Almost $48,000 has been raised after the family set up a GoFundMe account where Mr Jennings was described as a "bright light extinguished too soon".
"William was known to bring light to any room he walked into, and his sense of humor was infectious," the family wrote on the fundraiser account.
"He was full of life and potential, and left a mark on everyone he met."
The family said the GoFundMe account had been set up to help bring their only son home and pay for funeral costs.
"The world needs to know what an extraordinary man he was - he was the light of our lives," Ms Jennings said.
His father added: "As we got the news the house has just been full of people just coming to tell us how much he meant, he meant a lot to so many people".
ATSB is set to deploy a full team and remain at the remote accident site for about five days to examine the role the plane had in fighting fires in the area.
"I do not anticipate the ATSB team will take control of the site until mid-next week - we have to allow forensic specialists to do their job first," ATSB's Colin McNamara said.
A contingent of 211 Victorian emergency management personnel was deployed to Queensland to help with the firefighting effort in the state.
"This is really a terrible tragedy and any support and assistance we can provide to those families and loved ones we stand ready to provide that," Victorian premier Jacinta Allan said of the Cloncurry crash.
12°C