The thumping sound of the twin-bladed Iroquois helicopter rotors will be heard over Tauranga for the final time on Thursday, with a group of local veterans all set for their last flight in a Bell ‘Huey'.

It's the last scheduled visit to Tauranga for the RNZAF Iroquois, which are to be retired on July 1 after nearly 50 years of service. They are being replaced by the Airbus/Nato NH90 helicopter.

Two RNZAF Iroquois fly veterans over the South Island last week. Photo: Supplied.

The helicopters are expected to arrive at Tauranga airport at around midday on Thursday, May 14.

Introduced into the Vietnam War in 1963, the Iroquois' reliability and versatility soon saw 5000 of the aircraft operating in South East Asia. Eventually, it would become the most widely-used helicopter in the world, and found many uses in New Zealand in civilian life.

The RNZAF is touring the country with the Iroquois and taking veterans for one final ride before they go out of service.

They are among the thousands of New Zealand servicemen who came into contact with the Huey in Vietnam, and later when the helicopter was brought into service in the New Zealand services.

The current RNZAF Iroquois fleet is six airworthy aircraft, seven that have been placed in long term storage and one partial training airframe – a total of 14 airframes.

Air Force holdings associated with the Iroquois include spares, ground support equipment and specialist tooling.

One Iroquois airframe will be transferred to the Army Museum at Waiouru and two aircraft to the Air Force Museum in Christchurch for public display purposes, along with a number of associated artefacts.

The partial airframe will be loaned to Nelson Marlborough Institute Of Technology (NMIT) for on-going technical training of future aircraft technicians and six T53 Gas Turbine Engines will be transferred to the RNZAF Ground Training Wing at Blenheim, also for training purposes.

As per government direction, the remaining 10 Iroquois airframes and holdings are listed for international sale on 20 April 2015 via the Government Electronic Tendering Service.

There is a significant degree of commercial interest, but as ex-US military technology, all transfers are subject to US State Department approvals and any future operator would also need to comply with applicable civil certification requirements.

Initial tenders close on July 31 and the competitive selection process should be concluded by October this year.