An Australian airliner was grounded after four baby pythons escaped from their container in the aircraft's hold.

The snakes, just six inches long, were among 12 Stimson's pythons being flown from Alice Springs to Melbourne.

At first it was thought the reptiles may have been eaten by the other snakes, but this was discounted after they were weighed on landing.

Passengers were transferred to other aircraft. The jet was fumigated but the snakes' bodies are yet to be found.

"They're not endangered so a decision was made to fumigate...if these snakes turn up they will be very much dead snakes," David Epstein of Qantas said.

It is not known how the snakes - which can grow up to a metre in length - escaped from their container.

They were being transported in the cargo hold of the aircraft in a bag inside a plastic foam box with air holes.

The passenger aircraft returned to service on Wednesday.