Updated to Yosemite, now on 10.10.1 and the external display disappeared. It’s running through a targus dockingstation displaylink. There is multiple post about the issue on dipslayLink forum, some users got it to work: http://www.displaylink.org/forum/forumdisplay.php?f=30/ Tried both running the lastest DisplayLink 2.2 and the 2.3Beta, none of them work for MacBook Air 2013. Ended trying installing