Ok I honestly don't know the difference, and there is no sarcasm in my response to this. What is the difference? I don't mind learning new things.
Overt is when People know theyre there and know, or atleast suspect that something is going on (like the "contractor" that got bailed out by CIA officials in Pakistan after he shot and killed two combatants. The contractor, named "Raymond Davis", was beaten and imprisoned by Pakistanis and admitted to being part of a CIA contract team there. Ultimately the CIA bailed him out and admitted that they did have former SF soldiers providing embassy and diplomatic security.)
Covert means that outside of a select few, a mission is entirely classified. A good example is the cliched "heart attack" prior to some ground breaking or silence shattering speech.
I would say, that overt action is more like our military action in Iraq, and Afghanistan. And your example of overt is actually (i feel) covert, since it was never ment to be overt.