Prices have not been this low in at least two decades.

It comes as air fuel prices have plummeted and seat capacity has increased by at least 7 per cent since August when Pacific Blue ramped up its trans-Tasman services.

Passenger demand has also been slowing, forcing airlines to stimulate an overcrowded market. Eight airlines fly the route.

Fares on Air New Zealand's website are as low as $276.87 for return tickets. The trick is to book one-way tickets on each of its Australian and New Zealand websites, avoiding a doubling of Australian surcharges which add markedly to the fare, especially in and out of Sydney...