It's launch day for Apple as the company's two new smartphones, the iPhone 6 and iPhone 6 Plus, will be available on a walk-in basis beginning Friday at Apple retail stores.
The new phones were announced earlier this month. They have larger screens, faster performance and come equipped with Apple Pay, a contractless payment service.
They start at $199 at most wireless providers with a two-year contact. Both phones will be available from AT&T, Sprint, T-Mobile, Verizon Wireless and other carriers and other authorized Apple resellers.
On Monday, Apple says it had more than 4 million pre-orders of its new smartphones in the first 24 hours, exceeding its initial pre-order supply.
The company says the phones will be delivered to customers starting Friday and throughout September, but many won't be delivered until October.
Apple's website had intermittent outages because of heavy traffic as orders began online.
The company said the 4 million orders set a new 24-hour record, beating the 2 million orders in 2012.
That was for the iPhone 5, the previous time Apple increased the iPhone's screen size.
The iPhone 5, 5s and 5c have screens measuring 4 inches diagonally. The iPhone 6 is 4.7 inches, and the iPhone 6 Plus is 5.5 inches.
Besides larger screens, the new phones offer faster performance and a wireless chip for making credit card payments at retail stores by holding the phone near the payment terminal.
A free update to Apple's iOS software for mobile devices was made available to existing users on Wednesday. The new phones will come with the update, known as iOS 8.