He is now in possession of the high-tech aircraft he will use to make the nearly 45,000km journey, including 26 stops in 20 countries across five continents.
And it's tiny.
Lachlan has been allowed to lease the Cirrus SR-22 aircraft, complete with inbuilt parachute system and anti-icing features, he will use for the duration of his 10-week journey, which he plans to start and finish on the Sunshine Coast.
Between now and his departure date, Lachlan has a lot of work to do.
He will have additional fuel tanks designed and fitted into the aircraft and will spend time flying in a range of simulated situations he can expect to encounter during his world flight.
His first major flight starts on Friday when he plans to travel around 4000 kilometres across Australia.
The flight will see him navigate from the Sunshine Coast to Launceston, via Alice Springs, before making his way back along the east coast of Australia over a seven-day period.
Being able to test-fly the plane he will use for his record-breaking attempt has eased the minds of Lachlan's mum and dad, Vanessa Sprague and Will Smart, about their son's ambitious goals.
For Lachlan, there has always been more to the trip than shattering records or a joy flight.
"I want to send a message to teenagers everywhere they can achieve their goals," he said.
"It doesn't have to be flying around the world, it can be applying for a job."
Fundraising for his trip, which is estimated to cost around $350,000, is proving to be the most challenging for the teen.
"We are very grateful for the in kind donations we have received," he said.
"But we still have some way to go."
If you would like to get involved in supporting a teen achieve a world record while inspiring thousands of others, visit his gofundme page www.gofundme.com/WorldYoungestPilot?
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