We already knew Apple sold — and upsold — 1 million iPhone 3GS devices opening weekend, but an internal memo shows just how big an event that was for AT&T. Massive summer blockbuster, thy name is iPhone 3GS.

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.

Now imagine how many they would have sold if MMS and tethering were ready, and they’d expanding their network to better handle iPhone traffic.

(What, the dead horse had it coming!)

[Via MacDailyNews, thanks to everyone who sent this in!]

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AT&T Memo Leaked — iPhone 3GS Makes for Best Selling Debut Ever