Recurring issue : is it possible to change the SSD of a MacBook Air, or put one when you own a model with a hard drive? Overall, the answer is yes , if you have a good budget.
As OWC is basically the only company to offer SSD for all models , I take it as an example, but other models exist.
MacBook Air 2008
The MacBook Air was the first computer (or almost) to propose a series of SSD on a part of the range. 64GB, PATA and with one of the first Samsung SSD. The performances were not huge, but it was (very) expensive. The hard drive version was offering 80GB, with an awful iPod drive (4200 rpm, a single platter hard drive). It’s PATA ZIF 5mm thick, quite rare.
OWC offers 60 or 120 GB ($ 160 and $ 320) with performances limited by the PATA, about 90 MB/s. No indications on the controller, but it is a priori Indilinx, considering the memory cache of 64MB. There are also models on Jmicron on eBay, cheaper and 32GB, it is to be avoided. OWC provides a USB adapter for the old hard drive.
MacBook Air 2008/2009 (9400M)
The second MacBook Air goes with SATA but with a proprietary connector. Basically, Apple used a second generation Samsung or a iPod 120 GB hard disk (4200 rpm).
OWC offers 90 GB ($ 160), 120GB ($ 195), 240GB ($ 340) and 480GB ($ 520). It is expensive but much faster than the original SSD or – of course – the hard drive. This is SandForce SF2181 on SATA 3 Gb/s, an good controller. Attention please : no USB adapter with this model.
MacBook Air 2010
For 2010 models, Apple only provides SSD. From 64 GB to 256 GB at best. This is usually the second generation Samsung models, or Toshiba.
OWC offers 120 GB ($ 160), 240GB ($ 300) and 480 GB ($ 630). In all three cases, they are SSD with a SATA 6 gigabits/s controller (SandForce SF2281) limited in practice to SATA 3 Gb/s (250 MB/s) in the 2010 models. OWC offers a USB 3.0 adapter for $ 20 more.
MacBook Air 2011
On the 2011 model, there is a SATA 6 Gb/s interface but only 3 Gb/s SSD. Apple offers 64 GB to 256 GB.
OWC offers the same as for 2010, the interface does not change : 120, 240 and 480 GB. A 180 GB model ($ 210/230) is also available, but only for 2011 models .
MacBook Air 2012
On 2012 models , Apple has changed its form factor. SSD from 64 GB SSD to 512 GB are available, and either a Samsung SATA 6 Gb/s controller (Samsung 830) or the SandForce SF2281 controller with fast memory (Toshiba). In both cases , very good SSD.
OWC offers 120 to 480 GB in SF2281. 120 GB ($ 170), 180GB ($ 230), 240GB ($ 300) and 480GB ($ 660). No USB adapters on these models, unfortunately.
Please note that other manufacturers may have ranges of SSD for MacBook Air, as Runcore . Finally , some « OEM » Apple SSD can be found on eBay from time to time.