Australia will continue leasing two Israel Aerospace Industries Heron unmanned air vehicles pending the arrival of the Northrop Grumman MQ-4C Triton.

The two aircraft are leased from Canadian firm MacDonald, Dettwiler and Associates, and the cost for keeping the aircraft operational in Australia for six years is about A$120 million ($105 million), says Australia’s defence ministry.

One aircraft is already in Australia for training purposes, operating in restricted airspace over the country’s Woomera range. The other aircraft will return to Australia later this year after completing operations with the Royal Australian Air Force (RAAF) in Afghanistan.

“The retention of two Heron aircraft will help create a robust development program to ensure RAAF is well prepared for the Government’s investment in the MQ-4C Triton,” says defence minister David Johnston.

In March, the Australian government said it would acquire the MQ-4C Triton, becoming the first foreign customer for the maritime variant of the Global Hawk.

Canberra has not specified when the Triton will be introduced or how many airframes will be acquired. The Triton was selected under Canberra’s Project Air 7000 Phase 1B programme, which is the unmanned element of the RAAF’s two-phased replacement effort for the Lockheed Martin AP-3C Orion aircraft.

In February, Canberra said between eight and 12 Boeing P-8A Poseidons would also be acquired under Phase 2B of the project from 2017. The combination of Poseidons and Tritons mirrors the joint manned and unmanned maritime force being acquired by the USN to replace its P-3C fleet.