Many land units have the ability to strategically airlift. You can find the ability on infantry and some other ground units as an icon that looks like a plane in the unit info window. To use this ability move the unit to a city with an airbase. Once their you can give another move order to any other city with an airbase and they unit will be airlifted to the location. Just be careful not to do so in a combat zone as they can be shot down by enemy fighters or SAM's.