It’s a fascinating game to compare and contrast the wide range of business class seats which are available these days. There are forward-facing ones, a forward/backward-facing “yin-yang” configuration (hello, British Airways) and various forms of “herringbone” – taking its name from the appearance of the seating when viewed on a plan from above.All are trying to achieve a fully-flat bed in the smallest amount of space. The fully-flat bed is deemed essential by travelers who want to sleep on night flights and maximize productivity so they can hit the ground running at their destination. Direct aisle access is also preferred, to avoid an awkward climb over your neighbor. At the same time, airlines want to strip out as much weight as possible from the design, since every extra pound adds to the fuel bill.Rather than design the seat from scratch, most airlines adapt the off-the-shelf products of the major seat manufacturers – of course, the exact specifications change not only from one carrier to another, but from one aircraft type to another.To complicate things, some airlines have different types of seats across their fleet of aircraft. Nevertheless, it’s possible to identify the main designs and the carriers you will find them on. Here is a look at the six seats that are commonly used by airlines on their long-haul aircraft.SUPER DIAMONDOwned by Collins Aerospace, the Super Diamond seat has proven successful for airlines around the world, offering direct aisle access in a herringbone configuration. The seat features a comfortable 78-inch fully-flat bed (on most airlines) with fully customizable positions.This is the seat chosen by British Airways for its new Club Suite, and it has been “customized” with the addition of doors (the first time the Super Diamond has had doors attached, at least to our knowledge). On the other side of the Atlantic, Canadian carrier Westjet’s version is set to debut on the airline’s 787-9 Dreamliner. The cabin, designed by Priestmangoode, has only 16 of the seats laid out in the Super Diamond’s 1-2-1 configuration, with adjustable privacy screens separating the two center seats.Passengers will also be offered a turndown service when they wish to sleep – and Westjet had a reputation for being a budget carrier! FOUND ON: Air China, British Airways, China Airlines, Hainan Airlines, Hong Kong Airlines, Qatar Airways, Westjet.      

APEX 
First manufactured by B/E Aerospace (which was later acquired by Rockwell Collins), the Apex seat has a staggered arrangement that allows it both to be fully-flat and provide direct aisle access. This is a less dense configuration than the Thompson Vantage XL product because, as you recline, your feet do not disappear under the table in front of you. On Japan Airlines’ Sky Suite 787, which uses the Apex, the seats are set in private cubicles, meaning little chance of eye contact with other passengers when sat down (an advantage unless you are traveling with a companion, or have taken a fancy to a stranger).As with most of the seats listed here, it has several preset positions and a massage function. What’s more, there is also room under the ottoman to store a laptop bag, saving you from having to reach up into the overhead locker. Found on: Japan Airlines, Korean Air, Oman Air        

CIRRUS
Originally made by Zodiac Aerospace, since acquired by Safran Seats, the Cirrus has become one of the best-known (and liked) business class seats. There are different variations of it since it debuted with US Airways back in 2009.All versions offer fully-flat beds and direct aisle access, and are in a 1-2-1 configuration, although some offer more room than others depending on the density of the seating. Air France has a (forward-facing) reverse herringbone layout, where window seats face the windows, while Vietnam Airlines offers a traditional herringbone configuration, with outside seats angled towards the window and middle seats positioned inwards. Found on: American Airlines, Cathay Pacific, Delta Air Lines, Finnair, KLM, Vietnam Airlines  

OPTIMA 
The Optima is a clever concept by Acumen Design Associates and Priestmangoode, manufactured by Safran Seats. It can be found on United’s 777-300ER and 767-300 under the name Polaris. United is adding, on average, one aircraft with Polaris seating every ten days from now through to 2020. The business class cabin is laid out across two sections in a 1-2-1 formation.Odd-number rows have forward-facing seats separated from the aisle by a side table, affording more privacy, while even number rows are angled towards the aisle in a herringbone formation.The seat is comfortable, even for the tallest of passengers. The recline position is controlled with a slider that can be pushed to go from taxi to fully-flat and back again in a single effort. If we had to nitpick United on anything, it would have to be in-seat storage. While there is a side cabinet as well as an alcove by the USB port in the seat in front for small electronics, that’s about it. There is space beneath the footwell for a small bag, although much of this ends up being storage for the bulky bedding. Found on: United

STELIA SOLSTYS
This seat, now manufactured by Stelia Aerospace, also offers a fully-flat bed and direct aisle access but has some added quirks. It has a staggered design, so your feet are under the fully enclosed table of the seat in front of you when reclined.Like most seats, the Stelia Solstys product on Emirates’ A380 offers several preset positions. Seats in doubles are either side by side or with a wide gap, both with an optional divider. Whether people will realize they will be so close to one another (or so far apart if traveling together) is a challenge for the airline. It would be difficult to hold a conversation across the gap in the latter configuration.What is odd about Emirates’ arrangement is that the seats have a different pitch depending on whether you choose an inner or outer one. If you go for an outside seat, you get more legroom both for sitting and sleeping, while inside seats have less space.  Found on: Emirates, Etihad Airways, Iberia, Vietnam Airlines. Note that Singapore Airlines has a similar seat, known as the Solstys III, while Turkish Airlines has a tailored version of this seat under the name Aurora made by Stelia Aerospace.      

THOMPSON VANTAGE XL
The Thompson Vantage seat has a staggered arrangement, with seats alternating between a left and right orientation. While each is fully-flat with direct aisle access, some are marginally farther from the aisle than others. It achieves this by having the footrest under the fully-enclosed table of the seat in front. This means that each passenger is either next to the aisle, or separated from the aisle by a side table.As a result, the cabin has quite a few quirks in its layout, not least the 1-2-1 and then 1-2-2 configuration of the rows. JetBlue uses this seat for a handful of its Mint suites, which were the first business class seats to offer full privacy with a sliding door in 2014. It has since been adopted by other airlines, not least Delta Air Lines with its Delta One suite, which also has a sliding door for total privacy.Philippine Airlines also offers a version of the seat, claiming to be the only Asian carrier to offer the bonus feature of the Pneumatic Comfort System. This adjusts the seat firmness and has a massage function. Found on: Aer Lingus, Delta Air Lines, JetBlue, LATAM, Malaysia Airlines, Philippine Airlines, Qantas, SAS, Swiss.