The Papua New Guinea Defence Force is the military organisation responsible for the defence of Papua New Guinea. It consists of three wings. The Land Element, a land force consisting of the Royal Pacific Islands Regiment, a small special forces unit, a battalion of engineers, and three other small units primarily dealing with signals and health, as well as a military academy, is concerned with defence of the nation on land. The Air Element is a small aircraft squadron; its purpose is transportation for the other military wings. The Maritime Element is a small navy consisting of four s, three ex-Australian  landing craft, and one . One of the landing craft is used as a training ship. Three more Guardian-class patrol boats are under construction in Australia, to replace the old Pacific-class vessels. The main tasks of the Maritime Element are patrol of inshore waters and transport of the Land Element. Papua New Guinea has such a large exclusive economic zone that patrols by the small Pacific-class patrol boats, which are often unserviceable because of underfunding, are ineffective, so the Maritime Element is heavily reliant on satellite imagery for surveillance of its waters. This problem will be partially corrected when all of the larger Guardian-class patrol boats enter service.