Tough times for airlines are proving a boon for travellers wanting a taste of luxury with a discount.

While cut-rate international fares in economy cabins have been a feature of the past six months, heavy discounting is spreading throughout the plane.

Airlines are scrambling to fill their premium cabins and thousands of dollars of business-class discounts are being offered on long-haul flights, and on transtasman flights where the sharpest premium cabin fares are now as low as half standard levels....