We knew from before the iPhone announcement that Apple was having trouble with iPhone 5s supplies, and we saw the proof just two days after the release when shipping times pushed out to "October". Word had it that the fingerprint scanner was causing production delays, which could be the cause of the problems. According to the Apple website, shipping times on the iPhone 5s have risen up to 2 to 3 weeks...Source: http://www.phonearena.com/news/iPhone-5s-now-shipping-in-2-to-3-weeks-could-it-affect-iPads-as-well_id48224
