iPhone 6 may be Apple's biggest launch yet

Apple is planning its biggest iPhone production run yet, according to a new report in The Wall Street Journal.

Citing anonymous sources, the Journal reports that Apple asked its suppliers to manufacture anywhere from 70 to 80 million 4.7-inch and 5.5-inch iPhones by the end of the year. Apple is betting big on the larger screen models, as larger smartphones, such as the Samsung Galaxy, have become increasingly popular. Those larger models have helped Google's Android overtake Apple's iOS as the most widely used mobile operating system in the U.S., according to ComScore.

The production run would be significantly bigger than the 50 to 60 million iPhone 5S and 5C units ordered last year, notes the Journal. The newer models, unofficially dubbed the iPhone 6, are expected to have metal cases and come in several colors -- like the 5S does -- said the Journal's sources.

However, previous reports have hinted at production problems that could slow the new iPhone's debut. Last week, an analyst reported that while the 4.7-inch model would be available in the fall, the 5.5-inch model may not be on the market until next year, due to rumored sensitivity problems with its touch panel.

The newest iPhone screens are also rumored to be made of durable sapphire glass, not Gorilla glass like the current models. Initial reports said that only the larger iPhone 6 would have it, but a YouTube video earlier this month purportedly showing an "indestructible" 4.7 sapphire glass panel, seems to suggest otherwise.

CNET also reported last week that the iPhone 6 might just be the thinnest yet, taking advantage of a 2-millimeter battery. Taiwan-based Digitimes also noted that Apple's desire to make the next generation iPhone the thinnest model ever opened the door to a host of other problems, such as reducing the thickness of components -- namely panels, chassis, and battery packs.