There are not a lot of controls that work really well. And a lot of the controls that do exist were fought for tooth and nail. That is the entire point of the book. :)

For example, the locks in place at each Titan II facility all had exactly the same code (1111). And they were left unlocked.

Regarding the accidents, here are a few examples:

Thule Airbase crash: https://en.wikipedia.org/wiki/1968_Thule_Air_Base_B-52_crash

Damascus incident? https://en.wikipedia.org/wiki/1980_Damascus_Titan_missile_ex...

How about the two hydrogen bombs that were accidentally dropped from a B-52: https://www.theguardian.com/world/2013/sep/20/usaf-atomic-bo...

Or what is probably the worst incident to date, the B-52 that caught fire and almost blew up with 75,000 people within the blast radius: http://articles.chicagotribune.com/1991-08-13/news/910328029...

The list goes on and on. That is the reason why the book specifically called out that it was a miracle we haven't had any (known) detonations.

Here is a list of the _known_ broken arrow events: https://en.wikipedia.org/wiki/United_States_military_nuclear...

Keep in mind that the article we're discussing is about a 53 year old event that was _just_ revealed. There are more of them -- we just don't know about it, yet.