Irish band U2 have apologised for a practice that was heard in the suburbs surrounding Mt Smart Stadium, where the first of two New Zealand concerts will be played tonight.

"We've been here for three days and sound-checking so we want to apologise if we've upset some local people," production director Jake Berry said yesterday.

"But it is what we have to do in order to start a tour, and to start here in Auckland.

"We may make a little bit more noise doing it but we certainly inject a lot more cash into the local community."

Mr Berry said the band had been told by a council staff member that they were within noise limits and a 10pm curfew.

"As far as we're concerned, we're within all the limits set by the guidelines of public entertainment."

The band had practised half the show on Tuesday night, he said. "We had a few minutes on stage. We've been on a break, you know. We need to get the cobwebs out a bit."

A 50m-tall "claw", which takes up half of Mt Smart's field, has been erected as a 360-degree stage, after which the "360o Tour" is named.

The new design means an extra 5000 seats have been added to the stadium, taking capacity to more than 50,000.

The set has rotating bridges and a giant video system and is being flown around the world in six 747 jets.

"It's definitely the biggest show ever to tour - certainly the biggest one to come to New Zealand," Mr Berry said. "A lot of tours have a lot of equipment, we just have a little more."

He said it took one day to completely cover Mt Smart's grass area with an aluminium "floor".

It took four days to put up the claw steel system and a further day to add lighting, sound and video equipment, but all the effort was worth it, he said.

"One of the reasons the structure is so big is the band were very, very concerned about the intimacy of the show.

"It's really improved the look of the stadium, don't you think? You feel like you're in a stadium rather than something with an open end at each end."

Two other identical stages being rotated from venue to venue are being set up in Australia, where the band play next.

Mr Berry said fans could expect a good time, with singing star Beyonce's husband, rapper Jay-Z, warming up the show from 7.30pm. U2 begin about 9.15pm.

"I think you're all in for a treat. It's an amazing package to bring back here."

Meanwhile, fans planning to fly to Auckland at short notice can expect to pay through the roof, NZPA reported.

Flights to Auckland from Wellington and Christchurch were all but booked out on both Air New Zealand and Jetstar for yesterday, today and tomorrow.

One business traveller paid nearly $1200 for a high-demand, early-morning Wellington-Auckland return flight after coming off a waiting list.

Air New Zealand said extra flights had been added because of the concerts.

"Flights are very full and understandably the cheaper seats have sold out, leaving fully flexi fares available," an Air New Zealand spokesman said.