I think it was MIA where we were parked and I was doing a walk around on our 727 when I saw the 727 next to us. Mexicana I believe. Odd bulges at the base of the wing's trailing edge. So I saunter over to figure out what I am looking at. Sure enough.. the rockets. Didn't look as though they had ever been fired. No smudges on the fuselage. But definitely an attention getter.. much like the gravel kit on the 737. Unique.