Apple (AAPL) took more than 2 million iPhone 5 preorders during the first 24 hours of availability, and demand has remained impressive ever since. The company ran out of launch-day preorder inventory in less than an hour, and U.S. carriers each ran out within 12 hours. Despite slipping delivery estimates for new orders, however, Apple is seemingly seeing continued heavy demand — delivery estimates for new iPhone 5 orders placed on the company’s website slipped back yet again on Wednesday to between 3 and 4 weeks. Including preorders, sales of Apple’s new iPhone are expected to total between 5 and 6 million units during the phone’s first weekend of availability. The iPhone 5 launches this Friday, September 21st, at 8:00 a.m. local time.