Soldato
Or
9/11
NORAD were conducting fairly normal drills.
The bigger reason for the lack of initial response was that no one had expected anything like it to happen, and the likes of the Air Force had not been concerned with air attacks happening within the US without them passing the borders (internally American air security was light, there had never been a real need for interceptors to be armed to deal with flights originating inside the border).
London Tube.
It was IIRC a small scale training excercise for management of one department, something done routinely.
On virtually any day of the year government departments, emergency services, security services, large public bodies such as TFL or the Nuclear industry will be running training drills for one contingency or another. You only ever hear about them if they're really large scale (IE hundreds of people involved in a public area such as the combined major incident drills the Police, Ambulance and Fire services run a couple of times a year), or something happens on that day that the CT's can latch onto.
U.S.S. Liberty.
Again, Israel, a country effectively in a near constant state of war readiness running naval drills...Not exactly unusual, especially in a country where virtually everyone is expected to be part of the armed forces thus they're constantly training up new personal who need to be drilled, trained and tested in exercises to allow evaluation of them individually and as teams.
Sinai air crash.
Again it's a smallish area, and the Israelis will likely be doing some form of exercises most days for training, they also do a lot of combined ones with personal and equipment from other countries (partly because they both buy and sell military equipment to a lot of other countries which means they need to evaluate their equipment, personal and tactics).
Using facts and logic in GD?
It'll never catch on...