The original MacBook Air's charger looks a little different than the L-connector MagSafe 1 that the later gen Macbook Air's have. Here's the first gen:
It looks like the actual plug interface is the same, just the external housing is different. The wattage is also 45w.
Are they interchangeable?
My MBA: Late 2010 13 inch.
Best Answer
Yes, this will still work. The situation you want to avoid is using the incorrect wattage.