Currently running El Capitan. Maximum supported is High Sierra, but I can't seem to find experience threads with OS' newer than that. Anyone with experience as to performance with High Sierra or newer unsupported OS, willing to share would be greatly appreciated 
Specs:
MacBook Air (11", medio 2011)
1,8 GHz Intel Core i7
4 GB 1333 MHz DDR3
Intel HD Graphics 3000 384 MB
Specs:
MacBook Air (11", medio 2011)
1,8 GHz Intel Core i7
4 GB 1333 MHz DDR3
Intel HD Graphics 3000 384 MB