Australia and New Zealand have long had an on- and off-again relationship. Now it is taking to the air.

Today I was interviewed by Brisbane's Radio 4BC on media speculation that the air routes between Australia and New Zealand could be treated as "domestic" flights. This could lower the ticket prices - but possibly increase tensions over customs and Immigration.

I was asked to put the Australia/ New Zealand relationship in a broader context. A book I have found particularly useful on this subject over the years is: Denis McLean The Prickly Pair: Making Nationalism in Australia and New Zealand, University of Otago Press, 2003.

There are more New Zealanders living in Australia than there are Aborigines. Almost one tenth of all New Zealanders (389,000) now live in Australia. The average New Zealander here enjoys a higher standard of living than the average Australian: he or she is better educated and better paid. (Only about 63,000 Australians live in New Zealand). Australians and New Zealanders make about 2 million short-term visits across the Tasman each year.

Ironically, just over a century ago all New Zealanders were given the chance to live in a greater Australia - and they turned it down. That option still remains in the Australian Constitution.

Britain's James Cook in 1769-1770 sailed the South Pacific looking for a "Great South Land". For centuries Europeans assumed that there must be a giant land mass in the south to balance the giant Europe/Asia land mass in the north. He reported that there was no giant land mass - just a variety of different sized islands in a huge expanse of water.

The British set about colonizing New South Wales and New Zealand. New South Wales was first because Cook reported that the local people were more pleasant: they were inoffensive and not given to cruelty. The few Maori Cook saw scared him (10 of the crew members on his second voyage in 1774 were killed and eaten by them).

The first reported exchange between New Zealand and Australia took place in 1793. Two Maori chiefs were captured and sent to Norfolk Island to teach the convicts how to make flax. The trip opened their eyes to the British way of life. They returned home with stories of the new opportunities. Younger Maori then volunteered to serve as crew on ships to Port Jackson. The New Zealand tradition of seeking a better life in Australia therefore began over two centuries ago.

In 1831, the jurisdiction of New South Wales was expanded to include New Zealand. The settlement of New Zealand was greatly helped by the Treaty of Waitangi on February 6 1840, when Maori chiefs agreed to give control over their territory to the British (although there were later very brutal wars between Maori and the settlers). In 1841, New Zealand became a crown colony in its right.

Except for some "boat people" who escaped from New South Wales, New Zealanders are proud that they never received any convicts. New Zealand's European heritage came from settlers who wanted to go to the country. They feel superior to the Australians. Early migration schemes boasted that New Zealand was "another England": a green and pleasant land suitable for farming - while Australia was parched and snake-ridden.

Throughout the rest of the 19th century, the Australian colonies and New Zealand each developed in their own ways, like spokes off the London hub. They often ran on separate but parallel tracks. For example, the Australian colonies and New Zealand all tried to restrict Chinese immigration (much to the annoyance of London, which regarded them as good and cheap workers in its colonies).

The most significant national decision New Zealand ever made was to jump off the bandwagon of Australian federation when it began rolling in a serious way in the 1880s and 1890s. New Zealanders had already developed by this time a sufficient sense of their own separate national identity. The middle class New Zealanders looked down on the working class Australian "mateship" culture. New Zealanders, from small town, small farming communities, did not like the brassy, show-off way that Melbourne and Sydney had developed.

No common sense of identity had emerged. To people outside the region (such as Americans) the people of both countries looked so similar. But the people themselves felt different. Australians campaigning for a national federation gave opportunities to New Zealanders to be represented at their constitutional conferences. But New Zealanders in the 1890s replied that transport across the Tasman was inadequate and they knew as little about Australia as they did about Africa. They feared that they did not have the money to keep political representatives based in Australia for months on end.

Meanwhile, there was a movement within New Zealand emphasising the need to remain separate from Australia. They could become "Maorilanders", with a distinctive national culture. During the rest of the 20th century, Australia and New Zealand continued their separate development - both from Britain and from each other. They wanted to retain their links with Britain but British interests were now elsewhere. London decided in 1973 that it would be better off in the European Economic Community (now European Union). Australia and New Zealand had to develop different economic ties. In 1900, 91 per cent of New Zealand's exports went to Britain; in 1950 67 per cent went, and in 1990 only 8 per cent went.

The Australian Constitution retains a provision enabling New Zealand to join the federation if it wants to. There are rapidly improving economic ties and the basic treaty governing Closer Economic Relations came into effect on January 1 1983.

In current economic terms, "you get big or you get out" - hence the amalgamations on Australian farming and industrial sites. It may well be that the forces of globalization will oblige the two countries to come together after all.

But there are still major cultural differences. As Mike Moore, the former New Zealand prime minister once said: "Always remember, the Australians are our best friends - even if we don't like them".