While Sprint managed to sell around 50k to 100k Palm Pre phones during the first three days of handset's availability, a record for the company, AT&T seems to have neared the million with the release of the iPhone 3GS, the latest iteration of Apple's mobile phone. We already previously learned that the company had seen “hundreds of thousands” of pre-orders for the device, yet it seems that the number of sold units was even larger than expected.

According to a recently leaked internal memo from the wireless carrier, which surfaced on Digital Daily, the iPhone 3GS sales during the first day of availability were off the charts. Apple announced soon after the handset reached the market that more than 1 million devices had been sold during the first days, yet AT&T hasn't announced an exact number of units until now.

Here is what said memo (which has been sent to the carrier's employees this week) states:

iLaunch day 2009 was one for the record books, as AT&T customers scrambled to get their hands on the fastest, most powerful iPhone yet.

Here’s a look at some of the milestones we achieved:

* Best-ever sales day in our retail stores
* Second-largest traffic day in our retail stores
* Most transactions processed via our IT systems in a single day
* Most upgrade eligibility checks in a single day
* Largest order day in att.com history
* Largest features sales day in att.com history

On this year’s launch day, iPhone sales exceeded sales recorded on 2008’s iPhone launch day, Black Friday 2008 and Dec. 26, 2008–all heavy-volume sales days. In fact, this year we surpassed 2008’s launch day sales at about noon Central time, and sustained our previous peak hour record, also set in 2008, for 11 straight hours.

Undoubtedly, one thing that helped the new iPhone 3GS see this impressive traction on the market was the popularity of the previously available versions, yet the sales volume will still remain in Apple and AT&T's record books for a while. The handset has all chances to establish itself as a king on the mobile phone market, following the tradition of its predecessors. For what it's worth, it will be rather interesting to see when the following version will become available, and what capabilities it will pack, as some expect the next iPhone to be 4G enabled.