The reason they did not allow it was probably because it was an unauthorized photo. BTW, this arrangement of fluid filled tanks in an airplane has nothing to do with chemtrails. They are used for testing new aircraft. The fluid is pumped from one side to another to test the airplane's abilities when weight of passengers is shifted from one side to another. If you are interested in chemtrail equipment, I have read of mechanics encountering mysterious equipment associated with the toilets in aircraft and leading to tubes along the wings and apparently protected and maintained by contractors who don't like other people messing with it or knowing about it.