MacBook Air components are officially non-user-replaceable, though third-parties do sell upgrade kits for the SSDs. The flash memory and battery are enclosed within the casing, with RAM soldered onto the motherboard. The flash memory, difficult to access, has a 128 MB cache and a mSATA connection (updated to a proprietary PCIe interface) to the motherboard.
The only time Apple Support didn't have the answer at the ready was when I called to ask about autoplaying video. The call was set up at 9:28 a.m., and I was on the line immediately with Tonya in Idaho. After we joked over our equally poor weather, she attempted to connect to my system remotely but could not do so (likely because of our office firewall).