The many war games and exercises scheduled for 9/11 caused normal hijacking responses to be delayed, and so allowed the attacks to succeed.
We'll examine this case as it's portrayed in "The Military Drills on 9-11: "Bizarre Coincidence" or Something Else?", by Four Arrows (aka Don Jacobs).
The first exercise he addresses is Amalgam Virgo. Here Jacobs suggests that this exercise was running on 9/11, and could have been used as cover for the attacks, but the references he provides don’t back him up. Read the details here.
The second exercise is Timely Alert II. This was scheduled for 9/11, but there’s a serious lack of evidence to show that it could have had any effect on the attacks. Here’s the story.
Next up is Operation Northern Vigilance. Supposedly this ensured that “jets were removed from patrolling the U.S. east coast and sent to Alaska and Canada”, but where’s the evidence for this influencing 9/11? Let’s take a look.
Tripod II was another exercise. However, this wasn’t scheduled until 9/12 and bore no relation to NORAD or the FAA. It’s not clear how this might have affected the attacks, however Jacobs does have one idea relating to its significance. Here are our thoughts.
Vigilant Guardian is mentioned next. This is the exercise commonly referred to as being all about hijacked planes, causing confusion at NORAD and the FAA, but where’s the evidence for that?
Now Jacobs tells us about Northern Guardian, which he tells us may have related to “simulating hijacked plans [presumably planes] in different sector”. But he presents no evidence for that, and as it involved fighters being deployed to Iceland, between late August and early December 2001, it seems neither especially coincidental or relevant to the attacks. More here.
Next on the list of Operation Vigilant Warrior, but what isn’t spelled out is the legitimate question over whether this ever existed at all. Read more on this page.
This is followed by Global Guardian, but whether it could have any effect on 9/11 is far from clear. Here’s the story.
And the last one on Jacobs list is the NRO drill, which he and others suggest affected access to US spy satellites. Pity there’s no evidence for that, though. See for yourself.
Jacobs moves on to mention “the obvious problem of not being able to tell the difference between real and drill blips on NORAD screens”. This seems to be part of a common idea that “false blips” used by one or more of the above exercises confused NORAD and the FAA, but it this really true? We don’t think so.
There’s still the issue of whether these are “too many exercises to be a coincidence”, of course, but then how many is too many? Especially when a list like this includes one exercise that may well not have existed (Vigilant Warrior), and two weren't running on 9/11 (Amalgam Virgo, Tripod II). While one might have been, but as it involves planes redeployed to Iceland it's unlikely to have had much effect (Northern Guardian).
Even more importantly, there’s a distinct lack of evidence for any of these exercises adversely affecting the response to 9/11, or even to contradict the official view that they actually helped. And without that, it’s hard to see how this argument is going to move any further.