Pretty sure they don’t take live nukes out on training missions. :-)
I know that there are some stories out on the web about one or two bombers having an unarmed nuke drop off unintentionally, back in the sixties, and or one or two stories about bombers or fighters crashing with a nuke onboard that would then have to be recovered.
I know that at one time or another we kept aircraft aloft with nukes for a 24/7 deterrent. I think our lethal boomer subs have pretty much taken over the 24/7 deterrent role.
The bad thing now is that a shipping container anywhere in the world could have a nuclear cruise missile onboard. Damn just damn. The stealthy Club K Container comes to mind. Hat tip to George Webb.
SOURCE: http://theamericanreport.org/category/home/gulftainer/