One of the probable reasons for the delay of iPhone 6 and iPhone 5S release date is the disappearance of of two key executive allies at Foxconn.

Foxconn or Hon Hai Precision Inc. is Apple's iPhone manufacturing partner in charge of mass producing iPhone 6 and iPhone 5S. With Foxconn's exec missing in action for most of the past year and his second-in-command departed from the company, Apple is left working with a new executive hired from outside the company.

The change of culture at the Asian manufacturer comes as Apple aims for a 2013 release date for both the iPhone 5S and iPhone 6, with the former intended for release as soon as the end of spring.

There are reports that claimed that Foxconn is rushing the production of Apple's smartphones by adding 10,000 line workers every week since late March.

"We have been very busy recently as we will start mass-producing the new iPhone soon," said a Zhengzhou-based Foxconn executive with direct knowledge of production plans, according to the Wall Street Journal.

Foxconn and Apple have worked closely on iPad and iPhone releases over the past several years, despite controversies regarding labour conditions. A number of Apple's competitors also use the same Foxconn factories, but media attention for the labour troubles has been aimed primarily at Apple.

Foxconn claimed last week that its financial slowdown was due to the fault of the iPhone 5, which is setting sales records, suggesting that Apple has begun shifting iPhone manufacturing to another factory instead, a trend which could continue with the iPhone 6.

Some of the rumoured features of the next iPhone are Retina or IGZO screen display, A7 quad core chip processor, iOS 7, 128GB internal storage, 13 mega-pixel camera, and longer battery life. The lack of NFC support on the iPhone 5 was one of the biggest criticisms aimed at Apple's smartphone.

The low cost iPhone 5S, on the other hand, is rumoured to sport a plastic casing, 4-inch screen display, dual core processor and 8-megapixel camera.