Domestic fares are going up on Jetstar flights. Air NZ domestic fares increased just two weeks ago.

Jetstar is increasing its domestic airfares by 5 percent, just two weeks after Air New Zealand announced the same thing.

The average price of domestic flights increased on Monday across all domestic sectors, Jetstar spokesman Phil Boeyen said.

"Average domestic fare increases are around 5 per cent. On our lowest fares, this is an increase of between $2 and $4 per one-way," he said.

Jetstar's fares remained "very competitive for domestic air travel", but the company had to adjust to market demands, he said.

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"We regularly review our fares and make changes based on market conditions, including rising fuel costs."

This follows a similar announcement from Air NZ two weeks ago. An Air NZ spokeswoman said it was raising domestic fares because it was unable to absorb the operational cost pressures such as labour, fuel, goods and services.

At the time, Boeyen said Jetstar had "nothing to report" on the topic of increasing prices.

"We are keeping an eye on it," he said. "It's something that we constantly monitor."

Aviation commentator and former Aviation New Zealand chief executive Irene King said on May 15 she expected Jetstar would "absolutely" follow suit.

"Their cost base is really no different to Air New Zealand," she said, and the weakening New Zealand dollar against the US dollar would push prices up.

HOW MUCH MORE IS 5 PER CENT?

A Jetstar return airfare from Auckland to Christchurch, booked a month from now, currently costs $103. A 5 per cent increase would add another $5.15.