Our MacBook Air came with 2GB of 1066MHz DDR3 SDRAM. Like the previous MacBook Air, the RAM is soldered to the main logic board. Upgrading the Air's RAM after purchase isn't possible. As the upgrade from 2GB to 4GB is only $100, I recommend going with the 4GB.
Photo by: Bill Detwiler / TechRepublic
Caption by: Bill Detwiler