NEW YORK (CNNMoney.com) -- Didn't -- or couldn't -- pre-order an iPhone 4, but still want one on Thursday, the first day it goes on sale? Get in line. Now.
Just don't wait outside an AT&T store.
While Apple (AAPL, Fortune 500), Wal-Mart (WMT, Fortune 500), RadioShack (RSH, Fortune 500) and Best Buy (BBY, Fortune 500) will have "limited quantities" of iPhone 4s available at their stores across the country on Thursday, AT&T (T, Fortune 500) stores won't start selling the new smart phone to walk-in customers until June 29.
The carrier will have phones available in stores next week "on a first-come, first-served basis while supplies last." Once its inventory runs out, AT&T said it will offer "the convenient option" of buying the phone and having it delivered at a later date.
At the other locations, the iPhone is likely to be in short supply. Apple said it sold 600,000 iPhones on the first day the phone was available for pre-ordering last week, the highest number of orders for an iPhone in a single day. By comparison, Apple sold about 1 million iPhone 3GS units in the first four days of availability last year.
Demand for Apple's new phone was 10 times higher than it was for the previous version, the iPhone 3GS, according to AT&T. The unanticipated demand crashed AT&T's servers, and there were a number of customers who were unable to pre-order the iPhone 4 last week. AT&T stopped accepting pre-orders after just one day, and still hasn't turned that feature on again on its website. It's waiting for Apple to restock its inventory.
Customers can still pre-order phones on Apple's website, but the promised arrival date isn't until July 14.
So for customers determined to get their hands on a phone this week, the retail camp-out is the best option.
Each year, as Apple debuts a new iPhone, the lines outside Apple's stores notoriously start days before the phone goes on sale. Those lines will likely be even longer this year, given the phone's scarcity and popularity.
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