When I hook up fuel/ammo to the hangar, it loads slots intended for drones.

Is it possible to have output signals indicating a drone from this hangar is out on mission?

Or is there a better way to ensure my drones have a home?

Thanks

Update:
I realized the hangar was outputting it's contents on a network. Wire an inserter and check for network contents less than a stack of fuel/ammo and I got it! Had to use yellow inserters otherwise the inserters are just too fast, or I guess you can override stack size. Either way, I think I figured it out.