ir New Zealand are currently promoting an offer that you - or your ancestors - may find hard to refuse: return flights between London and Auckland for pounds 280 plus tax. The only catch being that you have to be aged 80 or more to qualify.

I find something obscurely heroic about Flight NZ1 (or its returning counterpart, NZ2). Every afternoon it shuttles out of Heathrow on its way to a country populated by our old friends and relatives. But don't be fooled by this quiet routine. We are talking about nothing less than the longest scheduled flight in the world. A 300-ton 747 that revs its engines in London today will, tomorrow, be sitting on the tarmac on a small island in the South Seas 12,000 miles away. Brothers and sisters who last saw each other at Southampton docks in the 1950s will be embracing. Arriving passengers will be on almost exactly the opposite side of the globe from where they had been the previous day.

In offering such cheap return tickets to frail old passengers - cynics may suggest - the airline is probably banking on not having to bring them all home afterwards. But this is to overlook the hardiness of today's elderly travellers. The last time I sat for 12 hours in the same seat (to Singapore just before Christmas) I seemed to be half the age of the average passenger. While complaining about the lack of leg-room in the back row, I was told by an elderly gentleman in the seat next to me that he had already flown to Australia and back three times that year.

Air New Zealand claim that the last time they carried out a similar promotion, a decade ago, the number of UK senior citizens tramping around New Zealand dramatically shot up. A 98-year-old who had never flown before suddenly found herself on the world's longest flight. We live in an age where a publicity campaign on the part of an airline can temporarily change the demography of entire countries.

At this point I admit that even cheap tickets for octogenarians would not have tempted my own grandmother to New Zealand. Born in 1900, her concept of overseas never extended much beyond the Isle of Wight and in common with the majority of the population of the world, she would never have strapped herself into an aeroplane seat. Looking a little further back - to, say, the second century AD - the obstacles to travel for the elderly were even more severe. The Roman emperor Trajan, energetic enough to annex most of western Asia to the empire, nevertheless wept upon reaching the River Indus that he was too old to see India. I can imagine just how painful that must have been.

But what excuse is today there for people born in Europe since the end of the First World War? As a habitual traveller, I find it hard to imagine that I will not want to take advantage of bargain flight offers when I am 80 (assuming I have not by that stage already died a traveller's death, swept away by avalanche, killed in crash, kidnapped by Rwandan rebels, etc).

At barely a penny a mile this fare may be the cheapest in real terms ever offered in human history. Those eligible, please take note.