The smugglers masterminded a scheme to fly a twin-engine Beechcraft aircraft to the historic gold mining town of Bulolo in the mountain ranges of Papua New Guinea's Morobe Province.
Two men piloted the unauthorised flight from regional town of Monto, northwest of Brisbane, to Bulolo.
After landing safely at the PNG airstrip, they loaded five duffel bags packed with methamphetamine.
Inside were 87 plastic bags containing a white crystalline substance weighing 71.5kg.
Testing later revealed the pure weight of the drugs was 56.98kg.
The men are alleged to have collected the meth and concealed it in the plane's nose cone before embarking on a "black flight" return to Australia - flying at low altitude with the transponder off in a bid not to be detected.
The cargo was bound for NSW, but when the return leg of the flight touched down in Monto on March 21, 2023 to refuel, the authorities were waiting.
Two of the five smugglers - co-pilot John Otto Horvath, 55, and 57-year-old Peter David Payne who provided ground support - pleaded guilty to a single charge of importing a commercial quantity of drugs in the Brisbane Supreme Court on Tuesday.
Two other syndicate members have previously been sentenced for their part in the elaborate scheme.
Justice Rebecca Treston said Horvath and Payne were far from the top of the syndicate hierarchy and had no idea of the quantity of the drugs the smugglers were bringing into Australia.
"I accept you did not finance any aspect of the importation nor were you particularly instrumental in the organisation of it."
Horvath was recruited for his piloting skills and stood to gain a slice of the profits.
"You had a significant role in the actual movement of the importation of the drugs," Justice Treston said.
"I accept you did not recruit anyone to the venture, and were in fact recruited yourself.
"But you helped fly the plane both to Papua New Guinea, allowed the collection of the drugs onto the plane, and then flew the plane back to Monto."
Payne lives next door to another of the smugglers and failed to grasp the extent of the importation plot.
"However, your conduct was more than objectively reckless, especially when you became aware of the true nature of the importation," Justice Treston said.
Payne did not hide his movements, used his own car to transport the fuel and even booked accommodation in his own name.
"It's probably best described as logistical support ... both of you were to receive a financial reward from your involvement in the drugs being imported into this country," Justice Treston said.
Horvath was sentenced to 15 years' imprisonment, with a non-parole period of 10 years.
Payne was handed a lesser sentence of eight years and will be eligible for release after five years.