You should be able to, since the d/c board of the system regulates the wattage th system takes, the higher wattage chargers you have will be regulated to the 35/45 the MacBook air takes.
Thanks everyone! I knew it shouldn't hurt as I have the 85W version for my 15" MBP and my wife uses it with her 13" MacBook. I was just worried about 1. The Connector, and 2. The almost double in wattage.
The MBA will only draw as much as needed, so no harm will be done. You can even charge a MBP with the MBA charger but it's not recommended since it will charge much slower and doesn't have enough power to both run the MBP and charge it at the same time.