Tim Cook unlocks the doors at Apple's Palo Alto store to kick off iPhone 6 sales

Cook participated in the local store's team meeting before doors opened at 8 a.m. And the CEO even took it upon himself to unlock the doors and allow the first customers in as the latest iPhones went on sale.

AppleInsider reader Benjamin was there and also saw Apple executive Eddy Cue at the store. He sent along pictures with both.

While talking to customers in line, Cook reportedly joked that he got his iPhone 6 "several months ago."

Another person took a picture with Cook using a Samsung phone, to which the CEO joked that they needed to buy a new phone. The customer indicated that they were waiting to buy an iPhone 6, and Cook told them that they would "have a lot better phone in a few minutes."

While Cook was onhand in the U.S., Apple retail chief Angela Ahrendts flew down under to Australia where iPhone 6 and iPhone 6 Plus sales began yesterday. Ahrendts was present when sales began at Apple's flagship Sydney location.

Preorders for both new iPhones reached 4 million units in their first 24 hours of availability. Apple's all-time record is 9 million iPhone sales in the first three days, reached last year for the launch weekend of the iPhone 5s and iPhone 5c.

Analysts on Wall Street generally expect that Apple will be able to exceed that number, and potentially top 10 million units, with the iPhone 6 and iPhone 6 Plus if the company can meet up with demand.

Gene Munster of Piper Jaffray surveyed the line at Apple's Fifth Avenue store in New York City and found that 1,880 people were waiting — a 33 percent increase over last year's debut of the iPhone 5s and iPhone 5c.

And Maynard Um of Wells Fargo Securities conducted a survey of early iPhone buyers at locations in New York, and found that more customers are opting for higher capacity 64- and 128-gigabyte models than in previous launch surveys. Of those who were polled, 67 percent said they planned to buy the iPhone 6 Plus, which carries a $100 premium over the iPhone 6.