When we click on a plnae in the 3D UI, it gets highlighted untile we click on another one. However, ocassionally it would be nice to be able to mark a plane that we expect to come back to shortly, after dealing with a couple of other aircraft (for example, after sending to hold at some intersection while waiting for a gate). Perhaps by clicking the mousewheel over a planes label, we could highlight it in a distinct color that would stay there until we click it again.