"Halfway to Papua New Guinea passengers reported seeing a snake clinging to the wing," a Qantas spokesman said of the snake, which is also known as a scrub python and can grow to as much as 8.5 metres (28 ft) long.
A crew member said the initial reaction when the python's presence was first reported was "you've got to be kidding".
The slithery stowaway was believed to have crawled onto the plane from scrubland or mangroves that surround the airport in tropical Cairns.
Qantas said there was no impact on the safe operation of the aircraft due to the snake's presence. The Bombardier Q400 was cleared to resume flying after it landed in Port Moresby.
The snake, unfortunately, was found dead on arrival.