The all-new 5.5in iPhone 6 Plus was announced with the new iPhone 6, but what will the bigger iPhone be like? Here's everything we know so far, including iPhone 6 Plus UK release date and specs.

The iPhone 6 is one of the most highly anticipated smartphones of the year. And Apple spoilt us this year with two new iPhones (neither of which was the iPhone 5C). As well as the iPhone 6, we find the iPhone 6 Plus. This catches up with the Android world as a large screen 'phablet'. See also: iPad 6 release date rumours.

We've gathered together all of the evidence to bring you everything we know about the iPhone 6 Plus so far, so read on to find out what the iPhone 6 Plus looks like, when the iPhone 6 Plus is coming out, and what new features the iPhone 6 Plus has.

If you want to find out more about the iPhone 6, which arrived alongside the iPhone 6 Plus, visit our iPhone 6 release date, price and specs story.

What is iPhone 6 Plus? iPhone 6 Plus specs and features

The iPhone 6 Plus is a bigger version of the all-new iPhone 6. It has a glass front that curves around the side to meet seamlessly with the anondized aluminum back, complete with stainless steel Apple logo. That display is what Apple refers to as 'Retina HD': albeit Retina Plus is 1920x1080, which on a 5.5in display equates to a pixel density of 401ppi - middle of the road for flagship smartphones. And, going back to build quality, Apple claims that the large-screen iPhone 6 Plus is a mere 7.1mm thick.

Apple says that the iPhone 6 Plus display hasmore than two million pixels, however. And Apple aims to differentiate its displays from the Quad HD screens we are now starting to see by saying that its colours are the key factor. Apple says the iPhone 6 Plus offers sRGB accurate colours. Apple also says the display has new, thinner backlights. And Apple says that the LCD is made with a tech called dual domain pixels, which allow it to have a very broad angle of view. The proof will be in the testing, of course.

What we did see at the iPhone 6 Plus launch was that the big iPhone offers an iPad-like layout for apps and content. There's even a horizontal home screen view. If you're in Safari, you can move backwards and forwards by swiping back and forth. This is a brand new gesture specifically for the iPhone 6 Plus, called Reachability. Double touch the Touch ID button, the whole display slides down so you can reach the top without taking your hand off bottom of display. Existing apps will simply scale up to the bigger display, although app makers will be encouraged to design new home pages for their software.

The iPhone 6 Plus comes with a new processors, known as the A8. This is a 20-nanometer 64-bit CPU with 2 billion transistors. Apple says it is 25 percent faster than the iPhone 5S' A7 chip, and offers significantly faster GPU performance. Consumers are likely more concerned that the iPhone is faster than Android and Windows Phone rivals. Again, we will test to find out. In a similar vein Apple also says power consumption is down, so battery life should be better. Indeed, Apple claims 80 hours of audio playback, and 12 hours of LTE browsing. Bold claims, but Apple is usually pretty honest with battery life. There's also a new version of the motion co-processor, the M8

iPhone Air release date: When is the iPhone Air coming out?

There's still no official release date for the iPhone Air. In fact, there's no confirmation that an iPhone Air is coming at all. But the evidence is mounting to suggest that the bigger iPhone is being developed behind the scenes at Apple, so we can certainly take a good guess.

After all, Apple CEO Tim Cook hasn't ruled out the possibility of a bigger iPhone. Back in April 2013, during an Apple earnings call, Cook said: "Some customers value large screen size, others value also other factors such as resolution, colour quality, white balance, brightness, reflectivity, screen longevity, power consumption, portability, compatible apps, many things."

"Our competitors have made some significant trade-offs in many of these areas in order to ship a larger display," Cook continued. "We would not ship a larger-display iPhone while these trade-offs exist."

That was more than a year ago, and since then technology has advanced to help eliminate many of those trade-offs. Take LG's LG G3, for example, with its stunning QHD display.

In December of 2013, Cook wrote that Apple has "big plans" for 2014, which could well be a sneaky hint at a bigger iPhone. He also says that he believes there are significant opportunities for Apple to expand the position of products such as the iPhone, and has noted that his statement that Apple doesn't aim to make the most smartphones has been misunderstood as him saying there will only be one iPhone at a time. The iPhone 5C is a clear example of that misunderstanding, as it launched at the same time as the iPhone 5S in September last year.

So with all of these comments from the head of Apple himself hinting at a bigger iPhone, the question is when, not if. Plus, there are numerous analysts and Apple watchers putting their money on an iPhone Air this year.

Most rumours point to a September unveiling alongside the iPhone 6, but the most recent rumour, which comes from respected analyst Ming-Chi Kuo from KGI Securities, suggests the iPhone Air could be delayed until 2015.

On 13 July, Kuo said that Apple is facing production issues for the iPhone 6, and that these issues are even worse for the iPhone Air. He therefore expects that Apple will push its launch back to 2015. At a push, Apple could choose to launch the iPhone Air in November this year, said Kuo, but he's not holding out much hope for that scenario.

We've heard similar rumours about the bigger iPhone delays in the past, but those were countered by later rumours that said the problems had been resolved. We'll have to wait for more information before drawing any solid conclusions.

If the iPhone Air does arrive with the iPhone 6, then according to Apple's invite 9 September will be the day it unveils the new iPhone ahead of a 19 September on sale date. However, Reuters suggests that issues with the display in the supply chain could push this back.

iPhone Air rumours: Design

The iPhone Air is expected to have a huge 5.5in display, which sets it up for the 'phablet' market. That's the same size as the LG G3's display.

The reason for the iPhone Air name, which has been talked about for a while now but was recently 'confirmed by a source' from China, is its thin and light design, apparently. Joining the iPad Air and MacBook Air, the iPhone Air is likely to particularly thin and light thanks to the use of new materials such as a sapphire display and liquidmetal chassis, which are stronger and therefore aren't required to be as thick.

According to DisplaySearch analyst David Hsieh, the iPhone Air will have a pixel density of 401ppi, compared with the iPhone 5S's 326ppi.

Alternatively, KDB Daewoo Securities says that the iPhone Air will have a 2272 by 1280 pixel display, which is 474ppi.

iPhone Air rumours: Leaked images

There are lots of leaked images of the 4.7in iPhone 6, but less of the iPhone Air, which could suggest that those rumours about a delay are true.

We have seen a photo of 'dummy models' of the iPhone 6 and iPhone Air side-by-side. While they're just mock-ups, they're pretty convincing, and are said to have been based on leaked specifications from Apple's factories. Plus, the come from previously accurate blogger Sonny Dickson on Twitter, so they could well be the real deal.

There's also a video of the mockups (below), compared with the iPhone 5s to give a better idea of what they'll look like and how much bigger they are.

As we near September, numerous leaked parts allegedly destined to make up the internal components of the iPhone Air have emerged.

In addition to the leaked images showing what the iPhone 6 and iPhone Air might look like on the outside, we've also seen a SIM card tray that could belong to the iPhone Air, and flex cables for the volume, mute, wake and sleep buttons.

The flex cables appear to confirm that Apple is considering moving the power button to the right of the device rather than the top where it has been located on previous iPhones.

Three of the SIM card trays shown in a photograph published by Apple.club.tw are blue, which sparked some suggestions that the iPhone Air may come in a new blue design. However, it's also possible that the parts are simply unfinished or belong to a prototype. Of course, it's just as possible that these parts don't belong to an iPhone at all…

At the end of July, we were also treated to a look at what could be the logic board for the iPhone Air.

There are also some concept images like the one shown at the top of this article, which was created by designer Gaétan Pautler. See more of his work here.