Link: 'Apple Announces Record Pre-orders for iPhone 6 & iPhone 6 Plus Top Four Million in First 24 Hours'

Apple Press Release:

Apple® today announced a record number of first day pre-orders of iPhone® 6 and iPhone 6 Plus, the biggest advancements in iPhone history, with over four million in the first 24 hours. Demand for the new iPhones exceeds the initial pre-order supply and while a significant amount will be delivered to customers beginning on Friday and throughout September, many iPhone pre-orders are scheduled to be delivered in October. Additional supply of iPhone 6 and iPhone 6 Plus will be available to walk-in customers on Friday, September 19 at 8:00 a.m. local time at Apple retail stores.

Just to put this into perspective, this is double the number of 'pre-orders within the first 24 hours' of the iPhone 5 from two years ago.