Hey All, it's Mrs 30taper (the OPs spouse)
Somehow, throughout this thread, the details he posted became a little, uh, cloudy.
We always travel with six bags total, typically three are checked @50lbs and three are carry-on. We have packed our gear - including the CCR tanks - in this manner for years and have had zero issues until this trip.
To clarify: We had already checked THREE bags prior to going through Mexican security. After the bleep-show with the young agent, we then had to check an additional TWO. One of these is overweight which when checked incurs an additional fee (which is why we carry it on.) He would not allow the bag containing the empty valveless COMPOSITE, eg lightweight, tanks past security.
While we were diplomatic right up to the end, it seemed to be out of spite that he refused the separate Pelican case. This held only regs, computers, lights, smbs - no cameras, housings, knives, or anything that might violate U.S. or Mexican security regulations.
Several times I had kindly asked to speak with his superior who, with a vacant stare, simply nodded and agreed with him.
We were completely caught off guard but had we been thinking more clearly, having an agent from AAirlines intercede might have saved at least part of the $350 in return baggage fees.
Wishing you better travel experiences along with a Happy Day!