Originally posted by FZ+
The simplest explanations are generally the best. Notice first a number of things. First, the shadow on the water is completely undisturbed. Secondly, we have a full curve of the suspension cables. This suggests the problem is more of an image anomaly.
Now, if we localise the problem, we can seen that it is a small oval shaped blurred area. It's tough to make out, but you can seen a little additional detail, that maybe connected. Look below the right tower, and you can see some small lines that overlay the shadow over water, and hence cannot do due to the suspension cables. Now, since this was from an aircraft, the camera is likely to be focused very much on the bridge. A likely explanation regarding the evidence is that the disturbance is caused by no more than a bird or insect flying with the camera's field of view. The line pattern overlay may also resemble a wing. This seems right now the most probable explanation. Of course, if god forbid a terrorist attack does occur, do remind me.