El Capitan on MacBook Air with 2 GB ram
The official system requirements from Apple state 2GB of RAM minimum. And as you have flash-based storage the paging to disk that many people see running RAM hungry apps will not be too bad. With any luck.

However I would be hesitant to recommend it as the newer the OS the more RAM hungry it seems to be. I would make a disk image of your current drive somewhere safe (external USB drive) so you can restore it easily if you don't like the results.