Apple says iPhone 5 preorders topped two million in 24 hours, more than double the amount of iPhone 4S preorders.
The company also says that while most preorders will be delivered on Friday, demand for the iPhone 5 exceeds the initial supply, so some of the devices are scheduled for delivery in October.
The iPhone 5 has a bigger screen - 10.16cm measured diagonally - that creates room for another row of icons and lets widescreen movies fit better. The calendar will now show five days at a time instead of just three. Previous iPhone models carried 8.89cm screens.
Apple says the iPhone 5 will be available in more than 22 countries on September 28.