About half of Apple's revenue comes from the iPhone, making the company susceptible to any problems with the device. Apple's fiscal third-quarter earnings fell short of Wall Street expectations in part because it shipped fewer iPhones than analysts had anticipated. At the time, the company said weekly phone sales were hurt by rumors of new products.
Apple introduced the iPhone 5 a couple of months after it reported third-quarter results. The new device is expected to help boost the company's results going forward, though its fourth quarter will include only a couple of weeks of sales. And since Apple introduced the device, there have been many reports of supply shortages for certain iPhone components.
William Blair noted that consumers have faced "significant delays" for the iPhone 5 since Apple released the device last month. As a result, it cut its iPhone estimates for the September and December quarters.
The firm now expects Apple to sell 26.5 million iPhones in its fiscal fourth quarter, down from its prior view for 33 million. For the fiscal first quarter ending in December, it expects shipments of 45 million, down 1 million from its previous forecast.
"Apple's inability to keep up with demand is being amplified by its aggressive global launch schedule and the company reducing its exposure to its traditional partner, Samsung," William Blair analyst Anil Doradla noted.
And Morgan Stanley analyst Katy Huberty said there's a wide range of potential outcomes for iPhone results, with timing of shipments and a ramp in display production acting as "major swing factors." She, for one, has decided to be more conservative with her estimates, modeling 25 million iPhones sold in the period.
Huberty also expects Apple's guidance for the current quarter to be weaker than analysts expect given iPhone 5 supply constraints and limited visibility into iPad Mini shipments. Apple sent out invites today for an event next week, which is expected to be the iPad Mini launch.
Meanwhile, Gabelli analyst Hendi Susanto also lowered his estimates for Apple's results to account for the iPhone 5 launch and weak PC shipment data.
While Apple doesn't generate as much revenue from its computers anymore, they're still an important factor in the company's results. Market research firms Gartner and IDC last week said PC sales were dismal in the recently ended quarter. Apple, which has been touting market share gains in the U.S., was immune to the decline, with its sales off about 6 percent to 7 percent.
Apple plans to report its fourth-quarter results after the stock market closes October 25.