Apple had an impressive debut for its iPhone 6 devices in the U.S. with record-breaking pre-order sales. AT&T had a role to play in Apple's success as the carrier broke its own record with its biggest pre-order launch day ever on Friday. The demand for the iPhone 6 and iPhone 6 Plus was so high that the carrier's servers stopped responding for most customers, forcing Apple to set up a reservation system to complete the orders. It took several hours for customers to finally sign back into the order page and get the order processed.

AT&T and Apple refrained from sharing the record-setting sales figure for iPhone 6, but it certainly will outbid last year's iPhone 5S demand. If the shipping dates are any indication, which show 7-10 days for the 4.7-inch model and 3-4 weeks for the 5.5-inch iPhone, Apple is already running short on supplies.

Apple distributed a total of 80 million iPhone 6 and iPhone 6 Plus units to Apple Stores, carrier outlets and retailers. This is in preparation for the big launch next Friday. Apple's iPhone 6 Plus demand is relatively higher compared to the iPhone 6 model, as the handset was running out of stock at most carriers and in Apple's own store before the inventory was re-stocked, according to a report by 9to5Mac.

Other carriers gave in to the overwhelming response by the customers on the launch night. T-Mobile's CEO John Legere acknowledged the downtime in a tweet. Sprint servers also failed to handle the rush in customers. AT&T came out a winner by holding up its online orders relatively well. The carrier confirmed the record-breaking pre-order sales in a press release on Friday.

"It was a terrific day for our customers and us. This is our biggest iPhone pre-order launch day ever," Glenn Lurie, president and CEO of AT&T Mobility, said in a statement Friday.