The military is considering using unmanned drones to patrol waters surrounding New Zealand.
At present, six Orion aircraft provide airborne surveillance, support for customs and police operations, search and rescue missions and disaster relief.
Illegal fishing and drug smuggling need to be watched for in New Zealand's Exclusive Economic Zone (EEZ), which is the fourth largest in the world and 20 times the country's land mass.
The Defence Force's P-3K2 Orions, which normally have a crew of 12 and also provide surveillance in the Pacific and Southern Ocean, are due to be retired from service in the mid-2020s.
A Defence spokesman told the Herald that a project examining replacement options was under way.
"It is still in the early capability definition phase. Remotely piloted vehicles will be considered as part of the project, along with piloted and space-based systems."
Australia will supplement the replacement of its own Orions with up to seven MQ-4C Triton unmanned aerial vehicles (UAVs), which have been under development by the United States Navy.
The drones, made by American firm Northrop Grumman, have the wingspan of a small airliner, weigh nearly 15,000kg and and are able to fly for more than 24 hours at a time.
State-of-the-art sensors provide a 360-degree view of surrounds, for more than 2000 nautical miles.
Australia won't rely on drones - new manned Boeing aircraft are the primary replacement for the Orions. The US will likewise use a mixture of drones and conventional aircraft.
Drone technology will have advanced by the time New Zealand replaces its Orion aircraft - Aurora Flight Sciences has built a drone that recently set a world flight endurance record for unmanned aircraft at 80 hours - and landed with 60 hours of fuel left.
Remotely piloted boats are also being developed. Singapore's Navy has unveiled its new unmanned surveillance boat, which is 16m long and can stay at sea for more than 36 hours.
Labour's defence spokesman, Phil Goff, said it would be important to keep surveillance options open for as long as possible, given rapid advances in technology. "To say that either drones or satellite technology could totally replace all the functions of a crewed flight would be speculative and premature."
Illegal fishing and other activities such as drug smuggling meant surveillance was important, Mr Goff said, and he was aware that Customs and Police weren't satisfied with the current surveillance capacity of the Defence Force.
Peter Greener, a senior fellow at Victoria's University's Centre for Strategic Studies, said UAV technology was needed - balanced with manned aircraft and satellites.
"You would want to maintain some manned capacity, both for working up in the [Pacific] Islands and providing search and rescue, for instance."
It was important to recognise that surveillance UAVs were very different from those used in combat, Dr Greener said.
UAV technology would be costly, and still require trained pilots and a control base, including technicians to analyse data. That meant there wouldn't necessarily be large savings or job losses, because personnel would be retrained.