The Ministry of Primary Industries is confident we won't have to turn around a plane over biosecurity scares.

The assurance comes after three car carrier ships were turned away from our ports earlier this month when hundreds of marmorated stink bugs were found on board.

MPI Passenger and Mail manager, Craig Hughes, says planes are easier to regulate than boats.

"The planes are a different beast really because not only are they cleaned regularly, but we also have a process called disinfection where they are sprayed to ensure that any flying insects in these planes and in the hold are killed or knocked down."

However he says incidents have occurred in the past - a legless lizard was once loose in the cabin of a flight from Australia and a pig was found in the hold on a flight from the Pacific Islands.

Hughes says fruit flies are a big concern but they haven't found any larvae in months.

He says there's much tighter control on planes.

"The good thing about aeroplanes is that they are easily sealed and easily cleaned, not like those vessels."