The Defence Force's new Poseidon aircraft begin patrolling the waters around New Zealand today.
It has taken four years of preparation to operate and maintain the P-8A planes.
Chief of Air Force Air Vice-Marshal Andrew Clark said the new fleet's introduction into service marks the beginning of a new era.
"New Zealand's maritime security is central to our survival and success.
"The Poseidon is the latest in a series of aircraft going back to the early days of the RNZAF that have kept watch from the air - securing our maritime resources, defending our region against military threats, building regional resilience, preventing trans-national crime, and of course carrying out search and rescue and humanitarian aid and disaster relief missions.
"In the Poseidon fleet, we now have the modern standard in technology to perform these crucial roles."
The Poseidons replace six 1960s-era P3 Orion aircraft, which have been in service for 57 years.
The four new planes cost $2.3 billion.
To accommodate the introduction of the new aircraft, No. 5 Squadron has moved from RNZAF Base Auckland at Whenuapai where the P-3K2 Orions were based, to Base Ohakea in Manawatū.