Reset Macbook Air without recovery key

IT guy here, got Macbook Air (don't know which OS) was purchased last year for one of my execs. He hasn't used it at all and brought it back doesn't know password and has lost recovery key. I am trying to reset this device to factory settings. I called Apple Support and am told without the recovery key it is a brick. I suspect this is not 100% accurate but checking here for thoughts, ideas, etc. Have proof of purchase. What are my options? No data on the drive just need to reset to factory. Just FYI in recovery mode the erase disk option is greyed out.