Model Identifier MacBookAir1,1 Model Number A1237 EMC 2142 Boot ROM: MBA11.00BB.B03 SMC 1.23f20 Macbook air with snow leopard 10.6.8 was bought. When I tried to upgrade OS X to Yosemite via Appstore it said This version OS X impossible install to this computer. I tried to install Maverick or Mountain Lion from DMG-file, but the answer was the same. Then I install OS X Lion from DMG-file and it was be installed. But anyway, some apps doesn't work in OS X Lion 10.7.5. Who knows, why I can't upgrade my Macbook Air?