Hm.
Don't think there's any such thing, I'm afraid.
Also, consider: if this command allowed a unit to never stop, wouldn't it just run straight through e.g. the aircraft? I'm pretty sure you can use playAction for instance to force a unit to walk up into an aircraft, as long as you position it correctly.
Sadly, units get stuck on minor things like bushes very easily when 'forcing' them to move. I've had this problem myself.
Wolfrug out.