Can I boot my 2011 MacBook Air from an external SSD (OS X, Windows and/or Linux)? I have a mid-2011 MAcBook Air which I just upgraded the SSD in.  The old SSD had a windows install which I have been unable to clone onto the new SSD (perhaps that is the solution I am looking for ...).  

Ideally, I would like to boot Win 10 from the external SSD - is this possible and if so can you point me to the right methods to get the current partition acting as a bootable drive?
If you have the old drive in an external drive case then connect it to your Mac and the hold down the option key at boot. The Mac will then give you the option to select the boot drive.