Having served in the Air Force for four years and having seen some of the security around USAF nuke storage bunkers and uploaded nukes on alert aircraft, al Queda would never succede in this plan. Way too much security. Even Air Force personnel aren't allowed to be alone around nukes. NO ONE is trusted around nukes. As for crashing into a supposed nuke bunker --- well, these are hardened to withstand quite a bit of force. This is assuming one can find a bunker with nukes in the first place.
It may very well be AlQaida SOP for nobody in a cell to know the true assignment until just prior to activation, and then perhaps only one person in the cell knows the true assignment and all the other cell members are given a different story.
I spent ten years in - all of it at Nellis AFB. Long ago, Area II used to be called "Lake Mead Base," and at one time, the local paper carried an article about how it was a nuclear weapons storage facility. When the 474th Tactical Fighter Wing was still active and at Nellis, Area II was listed (in the public domain) as the largest nuclear weapons storage facility in the west.
You're not kidding about the security around nuclear weapons. Would have been interesting to see anyone try to get to them at Nellis.