"Rather than screen everybody we now screen those most likely to pose a risk. I would rather have our MAF take a very good look at the bags they think might present a risk," he said.
The system was based on "intelligence and risk profiling" said Key and he believed it was the best option for assessing risk and delivering a better service to passengers.
However, he accepted it was impossible to check every item coming into the country and breaches did happen.
Under the new system staff continued to use a number of other measures including pre-screening to check bags coming into New Zealand, said Key.
The move away from full x-ray services aimed to reduce the wait time from about 28 to 14 minutes for transtasman passengers.
Another step in that direction has been the introduction of SmartGate, allowing electronic passport clearance of passengers from Australia.