The iPhone 4S made its official debut in the United States on October 14th and the device is still flying off of store shelves, Deutsche Bank analyst Chris Whitmore said Monday. “Demand continues to track very strongly,” Whitmore explained, citing checks with multiple Apple retail stores. “Apple is experiencing daily stock outs at ~85-90% of the ~30 retail stores we called,” he explained. “Apple employees are directing customers to make an online appointment (first come first serve) for next day pick up at nearby Apple retail stores as stocks appear to be refreshed daily at most locations.” We are not surprised by Whitmore’s findings. Canaccord Genuity recently found that the iPhone 4S was the top selling smartphone on AT&T, Verizon Wireless and Sprint during the month of October. Whitmore expects Apple to sell 28 million units during the quarter.