I misinterpreted what you were asking. What we were talking about is, if you hit the hangar with say, 1500 lbs of damage, that damage will repair itself after 7.5 minutes. If you hit it with another 1282 lbs before that 7.5 minutes is up, it will be destroyed.
While a building is destroyed, the downtime is the downtime. Town and other objects can be resupplied knocking 10 minutes of downtime off of them with each supply, but that doesn't apply to hangars. Hitting an object while it's down does nothing.
Wiley.