Air New Zealand is increasing fares on international routes by up to 5 per cent.

Some long-haul fares will be pushed up by more than $100 and the airline is blaming the increases on higher operating costs. The increases come into force from Thursday.

In advice to travel agents, the airline said fares on flights to the United States, Canada, Argentina and Asia would increase by an average of 3 per cent on all levels as well as the introduction of a day-of-week special surcharge of $30 or $60 for travel on Friday, Saturday or Sunday.

On the Tasman, Air New Zealand is pushing up prices from $10 one-way for economy saver fares, $20 one-way for economy flexi and premium economy; and $30-$40 (for Perth) in business premier.

A day-of-week ''Q surcharge'' of $10 on the Tasman would also be introduced on Monday, Thursday, Friday or Sunday on economy and premium economy. The Q surcharges don't apply to business-class fares.

Such surcharges can be used to encourage travel on less busy days and can be removed quickly if airlines face customer resistance and they move to other carriers.

For travel on Air New Zealand to the islands, most destinations except Bali and Hawaii will increase from $10 one-way for economy fares through to $40 for business premier.

All islands, including Bali and Hawaii - where Air New Zealand faces intense competition - will be subject to a Q surcharge of $10 one-way on Friday, Saturday or Sunday on selected seats.

The airline has been battling steep increases in fuel prices during the past year. During the last 13 months jet fuel prices have risen by more than 50 per cent.

Around the world other airlines are also pushing up prices as rising fuel and other costs take a 12 per cent bite into forecast revenue this year.

The International Air Transport Association forecast the airlines fuel bill would rise to US$188 billion ($267b) this year, well up on the US$156b estimated at the end of last year.

Airlines are also being hit by higher labour and en-route costs such as airport charges.

Across the industry fuel makes up 24.2 per cent of operating costs but for airlines such as Air New Zealand, which flies a high proportion of long-haul routes, it comprises more than a third of expenses.

Last month Air New Zealand and Jetstar both put up base domestic fares by 5 per cent.

In the United States domestic routes are attracting surcharges of between $3 to $7.50.

Fuel surcharges on Cathay Pacific flights bought in New Zealand rose from $20 per sector to $24 at the beginning of the month.

While the trend for fares is up, there are still promotional deals about, particularly on routes where there is strong competition.

At the weekend, return fares through travel agents to Europe dropped below $1000.

A House of Travel sale yesterday featured fares to Paris for $999.

The agent's commercial director Brent Thomas said Europe, Hawaii and Bali air fares were especially popular, as were cruise holidays.

Numbers at a House of Travel sales event on Sunday in Auckland were up from 3000 to 3500.