The 5.5-inch iPhone 6 is again rumored to face some production issues that may delay its launch or limit its availability.

Dubbed the iPhone Air, this purported 5.5-inch iPhone 6 model has been rumored to face delays before, although those claims were later refuted. More specifically, some previous reports claimed that the iPhablet was posing some production challenges, as component makers had a hard time complying with Apple's requests for the thinness of the battery unit. In light of those news, the 4.7-inch was expected to launch first, with the 5.5-inch model set to follow afterwards, maybe even as late as 2015.

Subsequent reports, however, claimed that Apple had resolved those issues and the 5.5-inch iPhone 6 was on track to launch alongside the 4.7-inch model, with no delays. The general expectation is that Apple will take the wraps off its next-generation iPhone 6 in September this year, which would fall in line with the company's previous launch cycles.

Fast forward to present date, and one analyst again believes that the phablet-like iPhone 6 model will face production delays or limited availability. More specifically, a research note from high-profile KGI Securities Ming-Chi Kuo notes that the issues Apple faces with the 4.7-inch iPhone 6 are even more serious with the larger 5.5-inch model, which could lead to delays. Kuo is a trusted source, as he has a good track record when it comes to the accuracy of his predictions in what concerns Apple and iDevices.

"The analyst believes that the 5.5-inch iPhone 6 may not launch by the end of 2014, or may launch after October in very limited quantities," Apple-centric publication MacRumors reports, citing Kuo.

According to the analyst, these issues cover technology related to the in-cell touch display, as well as issues with the handset's metal casing. The purported scratch-resistant sapphire cover glass for the 5.5-inch iPhone 6's display may not be able to "easily pass the drop test near term," Kuo further noted, this time cited by Apple Insider.

"Kuo said that the 'most conservative scenario' is that Apple delays the 5.5-inch 'iPhone 6' model to 2015. In that situation, he expects a larger 4.7-inch model along with more affordable iPhone 5s and iPhone 5c models will spur Apple to sales growth in the holiday quarter, meaning a later-than-expected launch for the rumored product would not have much of an effect on the company's bottom line," further reads Apple Insider's report.

Moreover, although a couple of videos purportedly showed off an extra-durable sapphire display cover for the 4.7-inch iPhone 6, Kuo believes that only the 5.5-inch model will use sapphire, and not even this is a given.

Despite all rumors, leaks, and reports, however, keep in mind that nothing is official at this point. As always in such cases, it's highly recommended to take everything with a grain of salt.