The easiest and most flexible way to add storage to a MacBook Air is plug in an external hard drive. USB 2, USB 3 and Thunderbolt drives are now available in all sorts of sizes and colours, not to mention weights, depending on whether you want portable or desktop models.
There is also an increasing number of wireless drives now hitting the market - generally in much smaller capacities than wired drives, but at least there's one less cable to have to think about.
USB flashdrives and SD cards provide yet another option, again generally in relatively low capacities, but these have the downside of sticking out of the laptop and taking up valuable ports.
Over the years I've tried just about everything. Different options for different scenarios, but I've long wanted a simple, cost effective and permanent solution to increase the maximum 256GB SSD drive space on my 13" 2011 MBA. And now I've found one!
The PNY 128GB StorEDGE Expansion Module (a 64GB version also exists) is specially designed for any MacBook that sports an SD slot. It is a bit smaller than a normal SD card and has a black plastic thumbnail grip to help push and pull it in and out of the machine. Once it is in the slot all that you can see is this 2-3mm edge, so the card is, to all intent and purpose, flush with the laptop. So it can stay there - pretty much permanently - without getting in the way of anything.
|StorEDGE 128GB MacBook Expansion Card|
Performance is not going to be as fast as other storage media, but I copied a 30Gb iTunes library from the MBA onto the StorEDGE in under 20 minutes. But if it's performance you're after you're missing the point - this is designed as a write rarely, read frequently device. It's ideal for iTunes, iPhotos, and other media files, work archives, and the like.
I couldn't find a UK supplier sadly. It's available from the US Amazon store but they won't ship to the UK. I got mine through eBay - where it cost $149 with $22 P&P. There was an additional $40 to cover import duty, so the total cost was about £130. Having placed the order on Sunday, it arrived 9 days later, much earlier than anticipated.
[UPDATE: I've since found a UK supplier, SCAN, who have the StorEDGE 128GB in stock. They charge £95.50 including next day delivery]
It is quite a lot of money to splash out - if you or someone you know is going to the US it would be worth getting one out there. However, this is a great solution for extending a MacBook without extra wires or another box to put in your laptop bag. And bear in mind that the price difference between a 13" MBA with 128GB of storage and one with 256GB of storage is £180.
Finally, please note that this is a dedicated expansion card, designed for MacBooks and it won't fit in your camera. Do not confuse this with cheaper and lower capacity SD cards which are also available from PNY and many other manufacturers.