The "airplane" strike on each twin tower featured a quick bright flash, right at the nose, just as it appeared to enter the wall. What were these flashes?
In trying to answer this, as usual, I wonder how I would create these video composites, and what problems I would have. After thinking it through, I know what the flashes were: Sync pops. They were a vital element in video fakery. Without the flashes, getting the 9/11 airplane composites right would have been far more difficult, and taken a lot more time.
Everyone has seen the countdown which precedes a motion picture. It ends when the counter reaches the number 2. On that exact frame, there is a bright flash, and often a beep tone. Known as a "two pop" or a "sync pop", the reason for having this flash is synchronization.
The video and audio elements of a show are created separately, and assembled together later. If a special effects artist created, say, a video composite sequence, he could deliver it back to the editor with a sync pop on the correct frame. The editor could then visually align that pop with the pop on his master, and he would quickly and confidently know that the effects shot was at the correct place on the timeline.
If I was in charge of the 9/11 video composites, I would not want to attempt to actually show an airplane hitting a tower in real time. I would insist that all live videos avoid showing that. This is, of course, the decision that was made for 9/11. Neither of the two live shots showed a plane hitting anything. For a theory of the live 9/11 videos, please see this. The present article concerns those videos which actually do show a plane entering the tower, none of which were live.
Without a flash, synchronization would be a major headache. We are going to insert a plane into various pieces of footage, from different cameras, at different angles. Presumably we've scouted the locations and done the test footage, and we've already got the airplane overlays done.
The angles and sizes match. But how do we determine where in time to place the airplanes? If the plane on one video enters the tower a little too early or a little too late, compared to another video, it could be a dead giveaway. For example, if there is a particular feature in the falling debris that is known to occur 123 frames after airplane impact, it had better be the same 123 frames later on all videos which show it.
As composi-traitors, we could try to use the same strategy, and key in on some identifiable feature, and work forward or backward in time. But what if there is no such feature readily apparent? Or if there is, what if one angle shows it, but another doesn't? And remember, we're under a deadline here. We need to crank out these composites as quickly as possible, and get them right. We don't have time to scour these explosion videos looking for a key piece of falling aluminum.
There is time code, which can be embedded into video and used to synchronize elements. But for this to be useful in this situation, we would need a live time code feed from a single master clock, going to all of the cameras as they are recording the tower explosions. This requires a satellite connection from the studio, and a pro camera. The idea is to pass off these videos as "amateur".
How will we know where in time to place the airplane sequence?
Enter the flashes. The flashes are very brief, lasting about 1 video frame, or 1/30 of a second. They make a very handy marker for where to place the nose of the airplane, in both time and space. On all of our prepared airplane layers, we have already designated a particular frame to be the one where the plane impacts the tower. In the editing software, we simply slide the impact frame to line up with the flash frame.
The flash frame also tells us when to begin erasing the plane with a mask. The flash frame is the last one before the nose starts to disappear.
The flashes on the 9/11 airplane videos are real. They are explosive detonations. They may or may not have been a necessary beginning of the huge explosions which followed. Either way, they were an essential element in synchronizing the airplane videos that fooled the world.