Around 2008 the Secretary of the Air Force and Chief of Staff were fired due to a massive screw-up regarding the transport and handling of our nukes [1].

The summary that I got from the situation was that a plane heading through the heartland of America accidentally transported a nuke, when instead they thought it was just some other type of bomb which basically means a nuke was accidentally transported across the US without anyone controlling the shipment or noticing until much later.

The current chatter and inclinations are that things have improved due to more rigorous checks and inspections. For me this is very believable due to the amount of news that is made when one of the nuke squadrons fail a regular inspection due to minor mistakes [2].

[1] http://www.airforcetimes.com/article/20080605/NEWS/806050301...

[2] http://www.airforcetimes.com/article/20130819/NEWS/308190013...