Want more legroom, extra space and a proper business class seat across the Tasman on Air New Zealand flights? We'll show you the best flights to pick and where you'll find more spacious planes with better seats.

Air New Zealand mainly uses small, single-aisle Airbus A320s in an economy-only configuration for its flights to NZ, but the Kiwi carrier also runs larger Boeing 747, 777 and 767 planes on certain routes.

Those have fewer people to clamber over, long-haul (and often more spacious) seats, and more of a chance of a spare seat next to you.

Air New Zealand's frequent flyers also get free upgrades to Premium Economy seating (better than regular domestic or trans-Tasman business class) on the 747 and 777 planes when booking economy. This benefit is also often extended to Virgin Australia's Gold and Platinum Velocity Frequent Flyers. 

And if you book full business class, you'll get actual business class rather than the more premium economy style "Works Deluxe" option on the smaller A320s, where you get an economy seat with a few inches' extra legroom.

Here's a quick primer on what Air New Zealand offers on its larger planes.

Real business class

In business class on Boeing 747 and 777 planes, you'll find Air New Zealand's top offering, Business Premier. That's a seat that reclines slightly or, if you want to take a nap, folds forward to make a fully flat bed for a good few hours' snooze.

The 777-300ER plane has the newest version, while the 747 and 777-200 have an older version of the same seat. All Business Premier seats have direct access to the aisle.

There's a full-sized work table, in-flight power and room to spread out. All in all, it's great for trans-Tasman business class.

On the Boeing 767, business class is recliner-style, in a 2-2-2 cabin layout, with a few inches more legroom than you'll find in domestic business class or across the Tasman on Qantas. (Plus, the middle seat pairs mean nobody climbing over you: a definite plus.)

Premium Economy

Air NZ hands out premium economy seats to its frequent flyers on trans-Tasman flights -- so if you're an Airpoints Gold or Gold Elite flyer, that's a big bonus. Some partner airline frequent flyers (Virgin Australia Velocity Gold and Platinum members, for example) also get this benefit.

In premium economy on the 777-300ER, you'll find the new Spaceseats -- which now have up to six inches more legroom than they did when launched earlier this year.

On the 747 and 777-200, it's a recliner style seat, which is less spacious -- but still head and shoulders above economy.

There's no premium economy section in the 767.

The best options for economy

Our pick for the best economy seats is the Boeing 747, with the 777-200 following behind. They have extra legroom (around 34 inches of seat pitch for most seats, three to four inches more than on a trans-Tasman A320 and as much as the top A320 offering, "Works Deluxe").

On the 747, these are laid out in 3-4-3 configuration, while the narrower 777-200 sees a 3-3-3 layout.

We're not fans of the new 777-300ER layout in economy, since there's an extra seat jammed into every row -- meaning narrower seats and narrower aisles -- and a couple inches less legroom than the old layout to boot.

How to pick the better seats and more comfortable planes

There are a few tricks to snagging yourself a better seat.

Check the flight number

The easy trick is to look at the flight number: If it begins 07, 08 or 09, it's an A320, but if it begins 01 it's a 747, 777 or 767. (Any trans-Tasman flights that start with 70 are codeshares with Virgin Australia's Pacific Blue operation.)

Check the Air New Zealand schedule and hover over the flight number for the days you want to travel.

You'll note that some flights change planes and flight numbers depending on the day of the week (the one around 1130 is NZ104 or NZ704, and uses a 777 or A320 accordingly).

Make sure your frequent flyer number is entered

Since high-tier frequent flyers get bumped up to premium economy automatically, make sure that your frequent flyer number is entered, whether your status is with Air New Zealand Airpoints, Virgin Australia Velocity, Etihad Guest, a Star Alliance airline or one of Air NZ's other partners.

Book on Air New Zealand's site

You'll only be able to select seats if you book via Air New Zealand (not via a partner), and have an Air New Zealand six-character PNR number (which should look like AB1C2D or something similar). 

We've had success getting automatically assigned to decent seats when booking via Virgin Australia with a Velocity Gold card (so double-check when you check in or, better, at the lounge) but you're likely to get the best seat by picking it yourself. 

For more trans-Tasman travel tips, check out:

• our guide to the best long-haul seats and service on trans-Tasman flights
• how to get into Air New Zealand regional lounges if you're a Virgin Velocity member
• full details of the Virgin Australia and Air New Zealand trans-Tasman alliance
• how the free wifi in Wellington's CBD works