iPhone first day sales likely topped 1.5 million units, according to estimates from Oppenheimer analist Yair Reiner. If his estimate is correct, Apple sold one and a half as many iPhones in the first day of availability as it sold during the first three days of new iPhone availability in 2008 and 2009.

Mr. Yair based his launch day sales estimate on 600,000 iPhone 4 pre-orders in the U.S., an average of 500 non-reserved units sold per Apple Store for another 100,000, about 50,000 iPhone sales for Best Buy stores, and then multiply by two for international sales.

If that formula proves to be accurate, Apple has already shot well past previous iPhone launch day sales figures. The numbers would aslo make this the single largest mobile phone launch to date.

Based on iPhone 4 launch day lines where some customers that reserved iPhones waited over ten hours to get in the store, Mr. Reiner’s estimates may not be too far fetched. Most of the wait time customers experienced was due to the volume of customers that needed to be processed, and not activation related.

The iPhone 4 was officially launched on June 24 to long lines of customers. Some customers that pre-ordered on JUne 15, however, began receiving theirs as early as June 22.

The iPhone 4 is available in black in a 16GB capacity for US$199, and a 32GB capacity for $299. A white version will be available later in July.

[Thanks to Fortune for the heads up.]