New Poseidon aircraft on the way

Australia is a big step closer to buying eight advanced Poseidon patrol planes from the US.

Under the deal worth up to $7 billion, Australia is buying the aircraft from the US Navy, which is in the process of acquiring them from manufacturer Boeing on Australia's behalf.

This is termed a Foreign Military Sale, where equipment is acquired through the US military.

Defence Minister David Johnston says these state-of-the-art planes will boost Australia's ability to monitor its maritime approaches.

The eight Boeing P-8A Poseidon aircraft will replace the RAAF's ageing Orion AP-3C aircraft which entered service in the mid-1980s and are due for retirement in the coming years.

The Poseidons will operate in conjunction with Triton unmanned surveillance aircraft and will be based at RAAF Base Edinburgh in South Australia.

Delivery of the first aircraft is set for 2017 with all eight to be delivered by 2018.