Flying

You are able to fly if you are a Aarakocran, are an immortal, or have
the fly spell cast on you. But common sense tells you that things
usually are not constantly in flight - they land to rest or sleep, to
enter buildings, go underwater where you don't fly but swim, and so on...

So, we have 2 commands, FLY and LAND. FLY lets anyone capable of flight
to become airborne. LAND takes anyone airborne and sets them back on the
surface.